7:02 Securing the gear shifter pawls (pegs) with cable zip ties will make it easier to insert the mechanism. Once the mechanism is in place, cut and pull out the cable ties with pliers. Makes the task a 10 second job.
Po osadení hláv ich len zľahka dotiahni, namontuj prírubu karburátora , s válcami sa bude dať hýbať ( určite bude pasovať aj tesnenie 😀) a hlavy dotiahni.
11:50 For the past 40 years, I've always used a piece mahogany placed across the right hand case and drifted engines back together using a lump hammer.
@@REBUILDLab A lump hammer is a heavy metal mallet used to hit chisels with, break open casting moulds, shift axle spindles & drift objects together or apart. They require very little hitting force to work as their mass imparts a good wracking force on impact, even with a gentle tap. More controllable than an ordinary hammer. Available from all good hardware stores. They come in 24 graduated weights.
34:00 Not a legend but fact!! The original 1986 - 1987 Jawa 350-638.0 produced 34 HP @ 6,500 RPM (redline at 7,000) and was capable of 155 KPH / 95 MPH fuelled by 99 RON leaded petrol (9.2 million calories of energy per litre). I've owned a 1987 638.0 and a friend owns two 1986 638.0 at the moment. Modern 98 RON E5 unleaded petrol contains only 8.5 million calories per litre so obviously they don't perform as they did in the past, but they're still a lot faster than the later restricted 638, 639 & 640 models.
@@REBUILDLab Wider piston skirt openings (restricted pistons don't fully open all 4 ports at TDC), longer silencers, no restrictor collar on the baffles (the plain one with no gasket is the restrictor) & no restrictive gasket opening on the carb manifold plus jetting differences. Unrestricted 34 HP & 6,500 RPM engines are marked * serial number *. Restricted 23 & 25 HP & 5,500 RPM piston engines ae marked ** serial number **.
@@CZ350tuner do you have any parts catalogue link, where the restrictor collar is shown, or some pictures, not sure about whether I have it or not (probably yes, then how does the unrestricted version looks like exactly...) Checked the stars on the engine, I have *number* version, so probably restricted.
@@REBUILDLab The unrestricted baffle has only to collars on it, both with a gasket. The restricted baffles (632, 638, 639, 640) have a third metal collar spot welded at the exit end of the baffle. The exhaust gasses have to squeeze through the 1mm. clearance gap between this metal collar & the silencer wall. It limits the power by choking the engine on its own gasses at high RPM. The restrictor collar can be either bent clear, to allow gas to flow freely past it, or removed by breaking the spot welds. The difference between the 34 HP * & 23/25 HP ** engines in pistons. Installing restricted narrow skirt opening pistons into an unrestricted * engine will reduce it to 27 HP, as it will still have the unrestricted long silencers attached. Opening out t he piston skirt openings, on a ** engine, so that all 4 transfer ports are fully exposed at TDC, will convert it to * specification (which is what I've always done to my own & other people's 638 engines). Unless the baffle is modified too, the engine will not make 30+ HP. The best home, for a 638 engines, is a 1970''s CZ 250-471 or CZ 350-472 bike, though the chain adjusters need to be heavily reinforced because they will rip the bolt out. (I've built 3 of these as café racers, so far, one for a friend).
@@CZ350tuner Very interesting, would you say that these stock bufflers, if they will be open up at the end with removing or bending the last collar plus open up the piston skirts for TDC gas flow and tuning the carb a little would bring nearly up to 10 hp? Now the engine is a 23 hp version. That could be worth a try. Another thing - do you experience the 638 engine running at least to some extent cultivated at constant city loads/speeds? For me that is the case only if the engine is at load, riding slow at higher gear 3th or 4th under load with low rpms. Otherwise its like all common two strokes, not really running smooth at low loads...
6:20 if the gearbox keeps destroying the 4th gear selector fork, it is caused by this bearing being misaligned & damaged by riding the bike with an over tightened chain. The only remedy is to change the bearing otherwise all replacement selector forks will also be destroyed within 100 kilometres of riding. I've repaired 9 engines with this fault.
Hi Andy, I have a 1974 350 (633/634) that doesn't go into 4th gear. In addition to the shift fork(s) which bearing should I be replacing? Appreciate this!
12;48 Before fitting the pistons, derestrict them by widening the skirt openings so that the transfer ports are completely open when the piston is at TDC in the bore, as with the original 1986 34 HP & 6,500 RPM 638. After 1987 the engines were restricted down to 25 HP @ 5,500 RPM via the piston skirt openings being narrower (partially blocks 2 of the 4 transfer ports at TDC), shorter silencer bodies and restrictor collars on on the baffles (no gasket collar at the tail of the baffle). I've been derestricting 638 engines for decades.
1a Arbeit ! Mir sind in den frühen 80ern im 360er mit 1:11 und 30er BVF oft die beschi..enen Pleuellager und Blech- Schaltgabeln verreckt, heute nat. kein Problem mehr. Mit den originalen Töpfen war nix zu gewinnen, mit denen von 150er ES / TS ging die Post dann richtig ab, 250 Emme im 3. kein Probem und das im -schweren- Pannonia Fahrwerk zu zweit.
Danke Jürgen! Du denkst also, das sman mit 150 Töpfen viel besser wäre? Wie hast Du die Gabeln und die Pleuellager geregelt? Habe eine Meldung vom anderen Zuschauer bekommen, dass die 350er Töpfe "restricted" sind. Könnte also was daran sein. Dies wäre auch eine Option dann...
Hi. Have you come across this problem? On my 2015 Jawa 640 oil is leaking from the gear box and collecting in the compartment where the gear box sprocket is. Some of it is entering the chain case too so at least I have a well lubricated chain! I've changed the the sprocket shaft seal and neutral switch seal to no effect. It'd not a huge amount but annoying all the same Does oil leak around the clutch pushrod? Any ideas? Thanks.
Hi, I would change the bearing and sealing ring, but the sealing ring should be temperature resistant. I did used viton one, holds for now. No, oil normally doesn't leak around clutcch push rod, as far as I know. This problem I had before the engine overhaul too...
Hi again. Finally fixed oil leaking round the pushrod. Just get a 14mm flat rubber washer with a 4.5mm hole and glue it into the recess at the end of the sprocket shaft using gasket sealant. Easy.
I got a 7 year old Jawa, engine never been touched. So I've got this shit still to come. Oh gee. So much bloody work. Should I add extra oil in the tank or trust the factory setting on the oil pump?
Hi Tom, for running in the engine must have extra oil approx 1:25 or so. Yeah, it is much work, but can be done in a couple of days, if you have the time to continuously work. Good luck 👍
@@REBUILDLab yes, the dealer tells you to add an extra 100ml to the first three tank fulls then just use the oil pump after that. You also get the carb needle sitting one notch lower to lean out the mixture after the first 3 tank fulls which is approx 500 miles. I've never heard of this on any other 2T bikes.
Can anyone tell me what PSI I should be getting on a compression test? I did a test on my engine when cold and I’m getting 130 PSI on the left cylinder and 135 on the right. I’ve done a bit of research on line and it’s hard to get an answer. It seems that two stroke twins typically have 170 + PSI, so I’m guessing that if it’s similar for a 350 twin, my compression might be a bit low
Hi, thanks for the question, can't tell really, have to measure it. But no time for it right now. I would rather concentrate onto symetry, so that both of the cylinders have the same compression pressure.
6:15 Jawa 250-623 & Jawa 350-633 engines don't feature the bearing securing washer & screw. It didn't appear on Jawa engines until 1976, along with a few other internal evolutionary changes, on the Jawa 350-634 engines.
DON'T USE SILICONE SEALANT IF THE ENGINE WILL BE USING ETHANOL CONTAMINATED FUEL (E5, E10, etc.)!! Ethanol dissolves silicone around the crank bay very quickly and will cause a leak to the gearbox, outside air, etc. Always use sealants stated to be ethanol resistant, such as Blue Hylomar. I've had to rebuild many Jawa & CZ engines because ethanol had dissolved the silicone sealant around the crank. CZ singles are affected the worst and will burn all the gearbox oil out through the crank. I've had 3 x CZ 125 engines, rebuilt & sealed with silicone, start burning gearbox oil within 200 kilometres, when E5 was first introduced in the UK. It took a while to figure out what was happening.
Thanks for the good tip, I have used a paper seal, silicone was only support. Not a good thing for the axial play, but for this it seems to be appropriate. I drove the engine for cca 1000 km already, seems to hold.
These videos are very, very good. Thank you! I have a 1986 638 TS350 that has a problem with hot starting which after checking every possible cause, I am thinking that the problem is due to lack of sufficient vacuum to suck through the fuel/air mix into the crankcase chamber. I can get it started by removing one spark plug and pouring some neat fuel inside. Someone has said that the problem is most likely to be the centre crankcase oil seal, but I cannot work out from these videos whether there is a centre seal or not. If there is no centre seal, I am wondering how the fuel/air mixture in one crankcase cycle does not escape into the other, or alternatively, there is not enough 'fuel/air charge' sucked in through the carb to enable combustion. i don't want to strip my engine down unnecessarily if the problem is due to something else. If you are able to help with any suggestions, that would be great :-).
Hi, of course there is a center crankcase seal, you cannot see it directly, because it is on the crankshaft center journal and one can change it after the crankshaft is disassembled only. You can see the outer side of it at 2:30 on this video. There are two bearings and in between of them there ist the sealing ring. But first, I would advise to change the carburettor, or overhaul it. Don't know your mileage on the engine, but if it starts with fuel inside, I guess it can be on the fuel mixture. It is really hard to tell, because there is so much that can influence the engine behaviour. Also check the ignition timing, spark plugs, air filter. And try to start with a starter spray sprayed into the carb before the start. If it comes, maybe you really just have to work on your carb... Maybe. Good Luck.
@@REBUILDLab Thanks very much for your reply. Is the sealing ring a rubber seal like on japanese two-stroke twins or is it a steel ring similar to a piston ring? I know that SAAB 95 and 96 two-stroke triple engines used steel piston ring type seals to seal the crankcases between each combustion chamber. This was a very good idea as it eliminated the problem of the rubber seals deteriorating over time. If the centre crankcase seal is of the steel 'piston ring' type, I wouldn't expect this to be worn before the bearings wear unless the engine has covered many miles/ran without oil/abused.
@@grahamfrancis9314 there is an aluminum labyrinth between the two crank center bearings with an oring from the outside as one can see. I would try the carb first, chinese can be bad, maybe the one I had could work, not perfect either, but usable. Then ignition timig, spark plug cables, cable ends and spark plugs, air filter, if nothing helps, only then I would dig deeper into the engine. But anyhow, my guess is the carb.
@@REBUILDLab OK. It makes sense what you say. I will try the new carb before I do anything else and then see what happens. Is there just the one O ring or two O rings each side of the aluminium labyrinth? My bike has a Powerdynamo conversion (which is great) and the ignition leads, plugs, coils are all good as far as I can tell. I'm also getting a spark. I will let you know what happens when I change the carb. Thanks very much for all the videos and commentary - these are really, really helpful.
27:40 WRONG!! Carb manifold MUST be attached and bolted into place on both cylinders BEFORE tightening down the cylinder heads, otherwise the carb manifold will not sit correctly with the cylinders and cause the carb manifold gasket to fail, allowing (false) air to leak in.
@@REBUILDLab I was caught out by this when I rebuild my first 638 engine in 1992. I had to loosen off the studs and redo the manifold block in order for it to seat straight & not to leak air.
Hi, sorry, don't understand a word. From google translate I guess you ask why the crank case was not heated up. Well, it was, with a heat gun. But it seems, that the new middle bearing housing is a little bit larger in tolerances, than it should be. As stated, this is not a guide, just how I did it. It would be better to heat up the whole crankcase in the oven, but I did not had the chance. And freeze down the crank simultaneously, but again no possibility for that...
Hm, čo dodať? Ako som to už spomínal, videl celý seriál. V podstate demontáž je jednoduchá. Cielené násilie dovolené. Montáž ma zaujala, už len preto, že cez leto som absolvoval. K tomu nahrievaniu: Ja som dal do mrazničky, ale kartre som zohrieval teplovzduškou. A neseklo ho pri vkladaní. Druhá polovica bola zaujímavejšia. Nesťahoval som, ale tiež nahrieval. Detaily nebudem rozpisovať. Inak sú tam nejaké komenty na motoride.sk, v príslušnom vlákne. . Farebná kombinácia tituliek je príšerná. Príliš sýte farby, nečitatelný výsledok(slovenské) Bude aj test drive?
Ahoj Jozef, dakujem za koment. Bolo to po prvy krat, tak preto tak trochu mimo. Jasne bude aj testovacia jazda, no pred tym hadam este montaz do ramu. No a na tu jazdu este nemam aparaturu ktorou by som to nejako rozumne nasnimal nech to nehega :) Vsetko dobre v novom roku inak :)
Hi XTZ600Z, I am not sure what you mean. A sport lightweight crankshaft is being mounted here. Neviem, co myslis presne. Montujem sem sportovu odlahcenu klukovku.
@@pazdzior18 Well, unfortunatelly not, it isn't I ordered it from a company some time ago, but they do not do it any more. It was made out of two old crankshafts, original material.
@@pazdzior18 no unfortunatelly it is not available, it is a custom build form a tuner, that does not do that anymore, I had to convince him to make this one and ha told me that this is the last one he made. Sorry
Ok, I used a translate machine and you say thi is how to not assemble a Jawa engine. Yes, you are right, this is no guide. but then again I explicitely claimed thi is NO guide. It is just how I did it back then. And I alos tryied to explain how to do that correctly in the comments in the video. Yeah, more kind of entertainment video...
cele zle a to co stvaral s klukou kolik na rotor altika konec :/ a hriadel bude kratsia urcite sak aj ledva jeden zavit sruba na rotor mu to drzala ....
No ked nechces nejaku nepodarenu repliku, co Ti ostava. Tento karb ma lepsie prechody, masina s nim zije aj pri poriadnych otoceniach rukovatou anie ako pri starom, ze na zaciatku trocha reakcie a potom nic. No ale ani tento nie je nejaka bomba, takze chystam presedlanie na upne iny karb. Uvidime, kedy sa k tomu dostanem.
@@REBUILDLab Ja zijem v Indonezii (ori z Trnavy).. Ked chces tak mi napis specifikacie a poslem ti (na vlastne naklady) pwk, keihin alebo mikuni karb🙏🇸🇰❤Su kurva drahe ale stoji to za to😉
@@georgeyoung4292 vdaka za milu ponuku, no mam uz kupeny tusim Mikuni to je, pouzity, ale mal by byt ok, neskor spravim nejake to videjko, teraz toho vsak mam dost, uvidime kedy sa k tomu dostanem. Ale predsa len by si mi mohol pomoct, a sice informaciou, co Ta motivuje pozerat tieto videa a co by pre Teba bolo zaujimave, co nemam... Vdaka
7:02 Securing the gear shifter pawls (pegs) with cable zip ties will make it easier to insert the mechanism. Once the mechanism is in place, cut and pull out the cable ties with pliers. Makes the task a 10 second job.
Thanks for ghe idea, Andy!
Po osadení hláv ich len zľahka dotiahni, namontuj prírubu karburátora , s válcami sa bude dať hýbať ( určite bude pasovať aj tesnenie 😀) a hlavy dotiahni.
Jo, to mi uz niekto tusim vravel, no nic - nabuduce :) Vdaka za podporu. Pekny den
11:50 For the past 40 years, I've always used a piece mahogany placed across the right hand case and drifted engines back together using a lump hammer.
Kind of hard to imagine. What is a lump hammer... dus you just hammerd the crank cases halves carefully together?
@@REBUILDLab A lump hammer is a heavy metal mallet used to hit chisels with, break open casting moulds, shift axle spindles & drift objects together or apart. They require very little hitting force to work as their mass imparts a good wracking force on impact, even with a gentle tap. More controllable than an ordinary hammer.
Available from all good hardware stores. They come in 24 graduated weights.
@@CZ350tuner clear, thanks
34:00 Not a legend but fact!! The original 1986 - 1987 Jawa 350-638.0 produced 34 HP @ 6,500 RPM (redline at 7,000) and was capable of 155 KPH / 95 MPH fuelled by 99 RON leaded petrol (9.2 million calories of energy per litre). I've owned a 1987 638.0 and a friend owns two 1986 638.0 at the moment. Modern 98 RON E5 unleaded petrol contains only 8.5 million calories per litre so obviously they don't perform as they did in the past, but they're still a lot faster than the later restricted 638, 639 & 640 models.
Good to know, I mean really, I didn't knew that. What is exactly the difference?
@@REBUILDLab Wider piston skirt openings (restricted pistons don't fully open all 4 ports at TDC), longer silencers, no restrictor collar on the baffles (the plain one with no gasket is the restrictor) & no restrictive gasket opening on the carb manifold plus jetting differences.
Unrestricted 34 HP & 6,500 RPM engines are marked * serial number *. Restricted 23 & 25 HP & 5,500 RPM piston engines ae marked ** serial number **.
@@CZ350tuner do you have any parts catalogue link, where the restrictor collar is shown, or some pictures, not sure about whether I have it or not (probably yes, then how does the unrestricted version looks like exactly...) Checked the stars on the engine, I have *number* version, so probably restricted.
@@REBUILDLab The unrestricted baffle has only to collars on it, both with a gasket. The restricted baffles (632, 638, 639, 640) have a third metal collar spot welded at the exit end of the baffle. The exhaust gasses have to squeeze through the 1mm. clearance gap between this metal collar & the silencer wall. It limits the power by choking the engine on its own gasses at high RPM. The restrictor collar can be either bent clear, to allow gas to flow freely past it, or removed by breaking the spot welds.
The difference between the 34 HP * & 23/25 HP ** engines in pistons. Installing restricted narrow skirt opening pistons into an unrestricted * engine will reduce it to 27 HP, as it will still have the unrestricted long silencers attached.
Opening out t he piston skirt openings, on a ** engine, so that all 4 transfer ports are fully exposed at TDC, will convert it to * specification (which is what I've always done to my own & other people's 638 engines). Unless the baffle is modified too, the engine will not make 30+ HP.
The best home, for a 638 engines, is a 1970''s CZ 250-471 or CZ 350-472 bike, though the chain adjusters need to be heavily reinforced because they will rip the bolt out. (I've built 3 of these as café racers, so far, one for a friend).
@@CZ350tuner Very interesting, would you say that these stock bufflers, if they will be open up at the end with removing or bending the last collar plus open up the piston skirts for TDC gas flow and tuning the carb a little would bring nearly up to 10 hp? Now the engine is a 23 hp version. That could be worth a try.
Another thing - do you experience the 638 engine running at least to some extent cultivated at constant city loads/speeds? For me that is the case only if the engine is at load, riding slow at higher gear 3th or 4th under load with low rpms. Otherwise its like all common two strokes, not really running smooth at low loads...
6:20 if the gearbox keeps destroying the 4th gear selector fork, it is caused by this bearing being misaligned & damaged by riding the bike with an over tightened chain. The only remedy is to change the bearing otherwise all replacement selector forks will also be destroyed within 100 kilometres of riding.
I've repaired 9 engines with this fault.
Hi Andy, I have a 1974 350 (633/634) that doesn't go into 4th gear. In addition to the shift fork(s) which bearing should I be replacing? Appreciate this!
12;48 Before fitting the pistons, derestrict them by widening the skirt openings so that the transfer ports are completely open when the piston is at TDC in the bore, as with the original 1986 34 HP & 6,500 RPM 638. After 1987 the engines were restricted down to 25 HP @ 5,500 RPM via the piston skirt openings being narrower (partially blocks 2 of the 4 transfer ports at TDC), shorter silencer bodies and restrictor collars on on the baffles (no gasket collar at the tail of the baffle).
I've been derestricting 638 engines for decades.
Do you have a pictures of this? I would consider to measure the power output before and after, if it's only a matter of skirt openings. Thanks
1a Arbeit ! Mir sind in den frühen 80ern im 360er mit 1:11 und 30er BVF oft die beschi..enen Pleuellager und Blech- Schaltgabeln verreckt,
heute nat. kein Problem mehr.
Mit den originalen Töpfen war nix zu gewinnen, mit denen von 150er ES / TS ging die Post dann richtig ab, 250 Emme im 3. kein Probem
und das im -schweren- Pannonia Fahrwerk zu zweit.
Danke Jürgen! Du denkst also, das sman mit 150 Töpfen viel besser wäre? Wie hast Du die Gabeln und die Pleuellager geregelt?
Habe eine Meldung vom anderen Zuschauer bekommen, dass die 350er Töpfe "restricted" sind. Könnte also was daran sein. Dies wäre auch eine Option dann...
Hi. Have you come across this problem? On my 2015 Jawa 640 oil is leaking from the gear box and collecting in the compartment where the gear box sprocket is. Some of it is entering the chain case too so at least I have a well lubricated chain! I've changed the the sprocket shaft seal and neutral switch seal to no effect.
It'd not a huge amount but annoying all the same Does oil leak around the clutch pushrod?
Any ideas? Thanks.
Hi, I would change the bearing and sealing ring, but the sealing ring should be temperature resistant. I did used viton one, holds for now. No, oil normally doesn't leak around clutcch push rod, as far as I know. This problem I had before the engine overhaul too...
@@REBUILDLab thanks. You mean the Bearing behind the oil seal? Where is the sealing ring? Sorry to be so thick.
@@TomBartram-b1c Yes exactly, the bearing behind the sealing ring...
Hi again. Finally fixed oil leaking round the pushrod. Just get a 14mm flat rubber washer with a 4.5mm hole and glue it into the recess at the end of the sprocket shaft using gasket sealant. Easy.
Je to tak napřed dotáhni přírubu karburátoru a pak dotahuj válce a hlavy jinak ti to bude dělat problémy,jinak pěkné video.
Vdaka za tip, Mirek!
I got a 7 year old Jawa, engine never been touched. So I've got this shit still to come. Oh gee. So much bloody work. Should I add extra oil in the tank or trust the factory setting on the oil pump?
Hi Tom, for running in the engine must have extra oil approx 1:25 or so. Yeah, it is much work, but can be done in a couple of days, if you have the time to continuously work. Good luck 👍
@@REBUILDLab yes, the dealer tells you to add an extra 100ml to the first three tank fulls then just use the oil pump after that. You also get the carb needle sitting one notch lower to lean out the mixture after the first 3 tank fulls which is approx 500 miles.
I've never heard of this on any other 2T bikes.
@@tombartram7384 yes, one has to run the engine on rich mixture too at the running in phase, so the needle must go up. After that it goes down again.
Can anyone tell me what PSI I should be getting on a compression test? I did a test on my engine when cold and I’m getting 130 PSI on the left cylinder and 135 on the right. I’ve done a bit of research on line and it’s hard to get an answer. It seems that two stroke twins typically have 170 + PSI, so I’m guessing that if it’s similar for a 350 twin, my compression might be a bit low
Hi, thanks for the question, can't tell really, have to measure it. But no time for it right now. I would rather concentrate onto symetry, so that both of the cylinders have the same compression pressure.
6:15 Jawa 250-623 & Jawa 350-633 engines don't feature the bearing securing washer & screw. It didn't appear on Jawa engines until 1976, along with a few other internal evolutionary changes, on the Jawa 350-634 engines.
Well, this one had it... Just the alignmeng was not good, not enough space for the washer...
DON'T USE SILICONE SEALANT IF THE ENGINE WILL BE USING ETHANOL CONTAMINATED FUEL (E5, E10, etc.)!!
Ethanol dissolves silicone around the crank bay very quickly and will cause a leak to the gearbox, outside air, etc.
Always use sealants stated to be ethanol resistant, such as Blue Hylomar. I've had to rebuild many Jawa & CZ engines because ethanol had dissolved the silicone sealant around the crank. CZ singles are affected the worst and will burn all the gearbox oil out through the crank. I've had 3 x CZ 125 engines, rebuilt & sealed with silicone, start burning gearbox oil within 200 kilometres, when E5 was first introduced in the UK. It took a while to figure out what was happening.
Thanks for the good tip, I have used a paper seal, silicone was only support. Not a good thing for the axial play, but for this it seems to be appropriate. I drove the engine for cca 1000 km already, seems to hold.
These videos are very, very good. Thank you! I have a 1986 638 TS350 that has a problem with hot starting which after checking every possible cause, I am thinking that the problem is due to lack of sufficient vacuum to suck through the fuel/air mix into the crankcase chamber. I can get it started by removing one spark plug and pouring some neat fuel inside. Someone has said that the problem is most likely to be the centre crankcase oil seal, but I cannot work out from these videos whether there is a centre seal or not. If there is no centre seal, I am wondering how the fuel/air mixture in one crankcase cycle does not escape into the other, or alternatively, there is not enough 'fuel/air charge' sucked in through the carb to enable combustion. i don't want to strip my engine down unnecessarily if the problem is due to something else. If you are able to help with any suggestions, that would be great :-).
Hi, of course there is a center crankcase seal, you cannot see it directly, because it is on the crankshaft center journal and one can change it after the crankshaft is disassembled only. You can see the outer side of it at 2:30 on this video. There are two bearings and in between of them there ist the sealing ring. But first, I would advise to change the carburettor, or overhaul it. Don't know your mileage on the engine, but if it starts with fuel inside, I guess it can be on the fuel mixture. It is really hard to tell, because there is so much that can influence the engine behaviour. Also check the ignition timing, spark plugs, air filter. And try to start with a starter spray sprayed into the carb before the start. If it comes, maybe you really just have to work on your carb... Maybe. Good Luck.
@@REBUILDLab Thanks very much for your reply. Is the sealing ring a rubber seal like on japanese two-stroke twins or is it a steel ring similar to a piston ring? I know that SAAB 95 and 96 two-stroke triple engines used steel piston ring type seals to seal the crankcases between each combustion chamber. This was a very good idea as it eliminated the problem of the rubber seals deteriorating over time. If the centre crankcase seal is of the steel 'piston ring' type, I wouldn't expect this to be worn before the bearings wear unless the engine has covered many miles/ran without oil/abused.
I have also ordered a new carburettor - probably will be a chinese copy :-/ But, it will enable me to eliminate this as a possible cause.
@@grahamfrancis9314 there is an aluminum labyrinth between the two crank center bearings with an oring from the outside as one can see. I would try the carb first, chinese can be bad, maybe the one I had could work, not perfect either, but usable. Then ignition timig, spark plug cables, cable ends and spark plugs, air filter, if nothing helps, only then I would dig deeper into the engine. But anyhow, my guess is the carb.
@@REBUILDLab OK. It makes sense what you say. I will try the new carb before I do anything else and then see what happens. Is there just the one O ring or two O rings each side of the aluminium labyrinth? My bike has a Powerdynamo conversion (which is great) and the ignition leads, plugs, coils are all good as far as I can tell. I'm also getting a spark. I will let you know what happens when I change the carb. Thanks very much for all the videos and commentary - these are really, really helpful.
27:40 WRONG!! Carb manifold MUST be attached and bolted into place on both cylinders BEFORE tightening down the cylinder heads, otherwise the carb manifold will not sit correctly with the cylinders and cause the carb manifold gasket to fail, allowing (false) air to leak in.
I'm with you, it would be better indeed!
@@REBUILDLab I was caught out by this when I rebuild my first 638 engine in 1992. I had to loosen off the studs and redo the manifold block in order for it to seat straight & not to leak air.
Добрый день. Почему не грели картера??
Hi, sorry, don't understand a word. From google translate I guess you ask why the crank case was not heated up. Well, it was, with a heat gun. But it seems, that the new middle bearing housing is a little bit larger in tolerances, than it should be. As stated, this is not a guide, just how I did it. It would be better to heat up the whole crankcase in the oven, but I did not had the chance. And freeze down the crank simultaneously, but again no possibility for that...
Very well done 👏👏💯
Love from INDIA
@@2downshifter Thank you very much, you're welcome :)
Good Video
Thank you Delta, you are welcome
Bardzo ciekawe filmy.
Thank you very much I really appreciate your words! You are welcome!
Hm, čo dodať?
Ako som to už spomínal, videl celý seriál.
V podstate demontáž je jednoduchá. Cielené násilie dovolené.
Montáž ma zaujala, už len preto, že cez leto som absolvoval.
K tomu nahrievaniu:
Ja som dal do mrazničky, ale kartre som zohrieval teplovzduškou.
A neseklo ho pri vkladaní.
Druhá polovica bola zaujímavejšia.
Nesťahoval som, ale tiež nahrieval.
Detaily nebudem rozpisovať.
Inak sú tam nejaké komenty na motoride.sk, v príslušnom vlákne.
.
Farebná kombinácia tituliek je príšerná. Príliš sýte farby, nečitatelný výsledok(slovenské)
Bude aj test drive?
Ahoj Jozef, dakujem za koment. Bolo to po prvy krat, tak preto tak trochu mimo. Jasne bude aj testovacia jazda, no pred tym hadam este montaz do ramu. No a na tu jazdu este nemam aparaturu ktorou by som to nejako rozumne nasnimal nech to nehega :) Vsetko dobre v novom roku inak :)
Bardzo dobra robota:) jak się nazywa taki zestaw do jawy, czy to Pana autorski projekt pozdrawiam serdecznie
Hi XTZ600Z, I am not sure what you mean. A sport lightweight crankshaft is being mounted here. Neviem, co myslis presne. Montujem sem sportovu odlahcenu klukovku.
It is my video of course, I made the work. Wel the crankshaft is a custom made one, not by myself, it is built to order thing from a company.
@@REBUILDLab hello, thank you for your answer, I meant whether the sports shaft is available for purchase or the whole set. greetings from Poland
@@pazdzior18 Well, unfortunatelly not, it isn't I ordered it from a company some time ago, but they do not do it any more. It was made out of two old crankshafts, original material.
@@pazdzior18 no unfortunatelly it is not available, it is a custom build form a tuner, that does not do that anymore, I had to convince him to make this one and ha told me that this is the last one he made. Sorry
هاي. هل موجود. بساتم. مال الجاو. ردلي. خبر. رجاء
Hi, again, don't speak your language. Sorry
هل موجود. جميع. أغراض المحرك. ردلي. خبر. رجآء
Hi, sorry, don't understand a word.
Как не надо собирать мотор Ява
Sorry, don't understand a word. English or German may be better, Thank you
Ok, I used a translate machine and you say thi is how to not assemble a Jawa engine. Yes, you are right, this is no guide. but then again I explicitely claimed thi is NO guide. It is just how I did it back then. And I alos tryied to explain how to do that correctly in the comments in the video. Yeah, more kind of entertainment video...
@@REBUILDLab I hake one million dollars ))
Бак внутри рыжий от отсутствия бенза и смазки ну а сборка движка быстрая однаао
Sorry again, don't understand a word. Anyway, you're welcome and thank you for the comment!
Que sigueñal es ese
Hi Jorge, sorry, don't understand...
@@REBUILDLab hablas Spanish
@@jorge4762 Sorry, dont't speak Spanish, just Engish, German, Slovak, Czech, understand a little Polish
Наяае638сначала затягивается патрубок а потом головки и прокладка под резинку дичь
Sorry, don't understand a word. Would be better to write in eng also for other readers. Anyway, you're welcome and thank you for the comment!
cele zle a to co stvaral s klukou kolik na rotor altika konec :/ a hriadel bude kratsia urcite sak aj ledva jeden zavit sruba na rotor mu to drzala ....
Ako pisem, nie je to navod. Dufam, ze ste si vsimli. Rad si pozriem Vase video na tuto temu.
mile rad by som zrobil ale uz jawku som predal nemam cas na to praca rodina a tak...@@REBUILDLab
@@filipsechny9502 Viem o com hovorite. No, tak sa drzte, rodina vie byt narocna vec...
این دیگه چه جور موتور جمع کردنه یا خدا 😂😂
Sorry, english, german, slowak only 🗣️
😳😳😳🤮
Told you this isn't a guide my friend
60€ za karburator je dost..
No ked nechces nejaku nepodarenu repliku, co Ti ostava. Tento karb ma lepsie prechody, masina s nim zije aj pri poriadnych otoceniach rukovatou anie ako pri starom, ze na zaciatku trocha reakcie a potom nic. No ale ani tento nie je nejaka bomba, takze chystam presedlanie na upne iny karb. Uvidime, kedy sa k tomu dostanem.
@@REBUILDLab Ja zijem v Indonezii (ori z Trnavy).. Ked chces tak mi napis specifikacie a poslem ti (na vlastne naklady) pwk, keihin alebo mikuni karb🙏🇸🇰❤Su kurva drahe ale stoji to za to😉
@@georgeyoung4292 vdaka za milu ponuku, no mam uz kupeny tusim Mikuni to je, pouzity, ale mal by byt ok, neskor spravim nejake to videjko, teraz toho vsak mam dost, uvidime kedy sa k tomu dostanem. Ale predsa len by si mi mohol pomoct, a sice informaciou, co Ta motivuje pozerat tieto videa a co by pre Teba bolo zaujimave, co nemam... Vdaka