Jawa 350/639 engine dismounting Part 4 (No Guide)
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- čas přidán 7. 09. 2024
- This is the 5. video from a series of Jawa 350/639 engine renewal videos. This time we are going to remove the crankshaft from the engine block, look at piston ring gap and compare the SERIAL crankshaft to a SPORT one.
Please note:
THIS IS NOT A GUIDE ON HOW TO DO IT!
Toto je 5. video zo serie o renovacii motora Jawa 350/639. Tento krat vytlacime klukovku z bloku motora, pozrieme sa na volu zamku vo valci a porovname SERIOVU klukovku so SPORTOVOU.
Prosim berte na vedomie, ze toto NIE JE navod ako na to.
Next parts:
Engine into the frame and Start
• Jawa 350/639 preparati...
Mounting the engine together
• Jawa 350/639 final eng...
Mounting deadmass compensating panels
• Jawa 350/639 engine mo...
Parts before:
Dismounting pistons and cut the engine in halves with a selfmade tool
• Jawa 350/639 engine di...
Dismounting primary gear and clutch
• Jawa 350/639 engine di...
Dismounting some basic parts, cleaning the engine
• Jawa 350/639 engine di...
Engine out of frame
• Jawa 350/639 engine re...
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Before installing new pistons,, open out the skirt openings so that they clearly expose all 4 transfer ports (for pre-charging) as with the original unrestricted 34 HP 1986 "Full Power" Jawa 350-638 engine. If you don't, installing the performance crank is a wasted effort, if restricted pistons are still in the engine.
Well, again, thanks for the tip. II did not checked that. It is not completely wasted effort, I can feel the engine is more agile. But this info is quite new to me. Just thinkin how to do it best with minimum effort now, after the engine already assembled... hmmm
The premature centre bearing wear, on 632, 638, 638 & 640 engines, is caused by running a 40:1 mixture on an engine originally designed for 33:1 mixture in 1986. The damage is caused by under lubrication.
have to switch to this, but I am affraid it can be too late now
Zdravím na Slovensko!!!Mám malou otázku,kde jsi sehnal upravenou klikovku+vložky a jaká byla cena.V ČR.to dělal Kasalický,ale nějak ty jeho úpravy zmizely.Dík za info!Jinak držím palce ať motor drží.
Je to od neho. Ukecal som ho, uz to nerobi. Boli s tym trable v tom, ze sa stracali presahy a trebalo dalsi zotrvacnik, ale ten strary, nie tie nove nahrady. No tak sa to nie len predrazilo, ale to bola aj posledna uprava, kt. robil... K Tvojej otazke, ak to fakt chces, tak sa treba obratit na neho s tym, nech Ti da kontakt na nejakych klukovkarov a tych treba ukecat. Prip. ved mozno ukecas aj jeho este, nevylucujem...
Мало. Хочется увидеть конечный результат. С таким коленвалом низы сильно просядут, но всё равно хочется посмотреть на то, что получится. Посмотрел ролик с удовольствием!
Hi, don't understnd a word, unfortunatelly. But thank you for the reaction of any kind. Have a nice day!
@@REBUILDLab Short video... I want to see the end result. With such a crankshaft, the traction at the bottom will be weak, but you still want to see the result. I watched the video with pleasure!
@@user-fg4gv8re4i There wan't be much of a power increase. But for sure it will be very very muc elastic. Maybe you can subscribe, I will post the end result in the future when it's ready and running. Have a greaqt day!
I would also like to know if you have already tried it, if I gain a little more revolutions per minute, how good it came out I find it perfect
Hi Hugo, thank you for the comment. Well it feels more responsive to the gas, I had problem with the clutch slipping after this, so stronger clutch springs are recommended. You will not achieve more revs with this, since the timing of the cylinder ports remained the same. The thing is to go faster through the available rev spectrum, to have better response, better acceleration, but no to have a race machine. For a racer you wold need to build a whole new crankshaft, modifiy the cylinder, carburetor etc... This crank is just modificated old one, which is not suitable for more power. And yes I tried it out, it has a better response of course, the power remained the same, the engine revs more enthusiasticly and it is overall more fun with the bike. Wher to find such crank...well you have to let it build. Unfortunatelly this crank was the last from the builder I know - he does not want to make it anymore. I suggest to find some crank restoration profis and kindly ask them to build some modificated crank for you. It can cost you up to 300 EUR for the mod only. Today maybe even more. Have a nice day.
@@REBUILDLab Please, I would like to buy it from you to buy it in the piece already made by you.
@@hugo.chacon I understand you would like to have the piece all ready made, completely understand that. But I do not do such services at this time and I am not sure how much would you like to pay for such thing. Because 300 EUR, that is only for the modification of the crank and that was I think 3 years ago I paid that mod. It would be much better for you, if you have the technical beckground and possibilities, to do it on your own. Just a good advice for you.
Good morning .. I would like to know how I can buy you a crankshaft like this already prepared
Good morning, honestly I don't know. This one was from Czech republic, from a specialist whom I convinced to make one crankshaft, because he didn't do it anymore. You have to find some specialist for crankshafts and convice him to do so. It is not cheap though.
I want parts 5 for mouting :)))
i have to reassemble the engine, but i don't know how? bearing in housing? bearing on crankshaft? how to do ?
Hi Lucas, it will take a while for me to process the videos. Basically the crankshaft cannot be overhauled at home, you need to give it to a specialist to change the bearings and balance it. Then you mount the center piece on the centre crank bearings and the engine block bearings with sealing rings. For the engine bearings to be mounted, you need to heat up the engine block to +90 C and cool down the bearings toi -18 C, then, they will just fall into the engine block. I will not show this at my videos though. Then the whole crank needs to be cooled down to -18 C and it should fall into the block bearing of the primary gear block halve. The other halve must be pull in through crankshaft. It is tricky and I have not done it like that which caused a lot of troubles.
Factory original heavy crank helps pull the Velorex 700 sidecar with children and wife as pillion. Torque over horsepower😀
Just try this one and you'll speak differently. It is another bike. You do not consume power to spin the heavy crank, you have the power on the wheel! 👍
@@REBUILDLab it would be easier and cheaper to just buy a Yamaha RD350😁 I was installing new pistons and rings in one of my Jawas and got out my Dremel to do some port adjusting like I did on my old formula one Suzuki 750 triple two-stroke when I thought to myself "you are going to change the ports on a bike with a 10:1 compression and which doesn't even have an automatic advance and retard ignition system? Don't be stupid and waste your time".
How much costs the RD 350? The problem is I like the Jawa...it has been in the family more than 20 years. Slowly I will get to it probably and do some more things to it, we'll see. Anyway, with this crank it is a while new motorbike, the engine is so elastic, can't believe it. Even if everything else is stock...
@@REBUILDLab An RD 350 in reasonable condition costs the same as a brand new Jawa 350 two stroke. I keep riding my sidecar TS my Red Style and my TS converted to a cafe racer😀
@@andrewallen9993 Thnx for the pricing, did not knew that. I am thinking of cafe racer style mod on my Jawa too, but have to do the GS 500 wrecked engine first :)
Tamamda bu krank nerede bulabilirim
Well, it is a custom build, you can't find it,. You can just find some good garage, that is restoring the crankshafts and let them make one as custom build. I would recommend to build whole new crank and not just modify the old one like I did. It can be made better, stronger...