JAWA 2-stroke power tuning (part 6) - how to make motorcycle gears

Yes, it has been a while. It simply took me 1.5 years of (re-)search, development und finally production of just a hand full of gears - some might say. But you better check everything twice if your own life depends on what you make.
This is the story of finally getting rid of one bigger blind spot on my JAWA 350 power experiment. The old gearbox that just stayed alive under the enormus load of a 47 Nm 2-stroke thumper. But with heavy pitting and - as it turned out - a bend main shaft.
This should now be over. Thanks to some historic JAWA MX competition parts. But mainly thanks to the grateful help of two Czech Specialists from motogears.cz who live their passion and convert it into reliable gearbox parts, which are better than the historic originals in most cases.
This by the way shows the reasons, why stronger gears were required for this bike:
• JAWA 2-stroke power tu...
And here is another insight of the MotoGears colleague capabilities if your like to see more on gear making:
• PĚTISTUPŇOVÁ PŘEVODOVK...
Enjoy this piece of #DIY workshop insight and as always, thanks for your comments.
Music by Peter Sandberg ‚An Unforgettable Moment‘

[@hffreebird]

Glad to see you back to it.

[@Q.L.Engineering]

Thanks Mate. And there is even material for more some parts. But I‘m not in a hurry…

[@meandthecat4025]

I got my father's first CZ250 sport in my garage. He passed sadly, so I promised him the bike would come back to life and Imma ride it forever. Can't wait to be building and developing my own engine. I might go for an I2 layout and make it a crossplane.

[@Q.L.Engineering]

All the best mate and good luck.

[@CZ350tuner]

The Jawa 350 & CZ 250/305/350 twins always needed a 5 speed gearbox, as it was very easy to redline the engines in 4th (top) gear. The only solution I found was to change my tuned 1976 CZ 350 motor's sprocket ratio from the stock 16:52 to 19:52 and replacing the original 13 tooth output sprocket shaft with the later 1978 CZ 250's 14 tooth version. Another issue with 1970's CZ350's is that of one identifies and removes all the restrictors limiting the power output to 22 HP @ 5,250 RPM, one soon discovers why they were installed when the increased performance rips the weld apart that attaches the bolt to the chain adjuster, also bending the swing arm chain adjuster lug.

[@Q.L.Engineering]

That‘s interesting, Mr. Reid.

[@javvak21]

Kyvku mám z DT125 :-) Nebo origo napínáky lze snadno předělat na excentry. Taky jsem jezdil. Neboť 350 má v lese příliž síly 😂

[@sczcz1625]

I love all the work. Who would though that somebody try to make Jawa actually usable 😄. And the wheelies are amazing!

[@Q.L.Engineering]

😀👍🏻👌🏻

[@mcficodjfico5944]

A lot can be learned from your videos. Kudos to you for your effort, knowledge and care for every detail. Very interesting content and channel. Greetings from a Jawa driver

[@Q.L.Engineering]

Thank you for that, Jawa driver.

[@petrnejedly4428]

Krásná práce😊

[@Q.L.Engineering]

Thank you!

[@rosifert]

Moc pěkná práce. Tento problém řeším stále. Mám Velorex 250. A je moc těžký na obyčejnou převodovku. Rád Vás sleduji.

[@Q.L.Engineering]

Ahoj. Možná můžu dát tipy. Moderní převodovky typu 634 je nejlepší nepoužívat. Mají méně kolíků (4 místo 6) na menší roztečné kružnici, což je nepříznivé. Pak je užitečné udělat primární překlad co nejdelší. S duplexním převodovým poměrem 579 je alespoň o pár procent delší. Převodovka se tak trochu namáhá. Pro kompenzaci nainstalujte menší sekundární pastorek. Obecně byste měli zkontrolovat, zda jsou všechny kolíky podepřené rovnoměrně. To je zřídka případ. Možná bude možné vybrat převody, které jsou lépe vyrobené. Používám k tomu „tubing pastu“ nebo speciální barvu.

[@arrbam02]

Fantastic work, lovely to watch. Wish we had more riding in the end, it runs so sweet!!

[@mensand5294]

I have watched all your videos , I had a 638 good bike 🏍️

[@Q.L.Engineering]

Thanks for watching and your comment!

[@jawadeepak]

Massive Respect from Tamilnadu 🙏🏾💥

[@Q.L.Engineering]

🤟🏼👋🏻💥

[@PHUSII]

New follower, nice machine work. I'm a machinist too and only a hobby moped tuner. I have a Tomos engined moped so I feel you when you need to make parts for yourself! :D

[@Q.L.Engineering]

Thanks Mate.

[@notagunfreak8146]

Awesome work!

[@Q.L.Engineering]

Thanks Mate 🤛🏼

[@gravydavy4188]

I should be asleep now, it's 2.30 am, your craftsmanship is beautiful so im going to keep watching. Thank you. 😊

[@caguairan.]

Buen trabajo, esa moto es una belleza

[@Q.L.Engineering]

That‘s right. Thank you.

[@robinsajan9384]

Waiting for more videos on jawa

[@SB-vb8ch]

Amazing work, I think I would have resorted to adapting the cases to take a complete gearbox from something else!

[@Q.L.Engineering]

Thanks, but that would be hard to combine with the obsession of stock bike look.

[@ManO0waR]

Шикарно!

[@Oldmz]

Woow 😍... such a great video ❤❤

[@Q.L.Engineering]

Thank you, Sir.

[@snrsmh]

Hi, this working is perfect congratulations 🎉

[@Q.L.Engineering]

Merci, Thank you. Regards.

[@SIMPL3_7495]

21:56 why u changed the exhausts

[@Q.L.Engineering]

They are better for daily rides Hasan.

[@4781gowtham]

Great work 😍😍😍 i am from india..

[@Q.L.Engineering]

👊🏼👍🏻Thanks for your comment!

[@isickofit]

"There's not much out there can beat a well sorted Jawa" Overheard, 1970s

[@Q.L.Engineering]

👌🏻👍🏻👍🏻🥰😁

[@isickofit]

@@Q.L.Engineering Suzukl left the chat.....

[@isickofit]

We know what they did.

[@Mike40M]

Great video. Reminds me of the days I designed 5 speeders for racing outfits. More tricks in gear making than meets the eye. Just one question. What sealant did you use?

[@Q.L.Engineering]

Quite normal high temperature silicone.

[@rebekahfrench5747]

Well that got technical.. 👍

[@Q.L.Engineering]

Yepp, thanks for your feedback.

[@rebekahfrench5747]

@@Q.L.Engineering this day and age no one fixes anything they just throw it away and move on.. old school mechanics are worth their weight in gold because they have the capacity to rebuild and overcome small issues.. how disappointing the younger generations have no idear how to fix a push bike let alone anything complex mechanical.. they find it too hard to learn..

[@Q.L.Engineering]

That is very true and unfortunately matches my average observation.

[@jawist71]

👍

[@Q.L.Engineering]

👍🏻👊🏼

[@jamest.5001]

I want to build a bike with a snow ❄️ sled engine on it, possibly use a gear box from a CBR 750-1000 or so, maybe find a damaged case cut the engine away from it, and weld up the gap, use a chain or belt to connect the two, a CVT between the two maybe interesting. It would likely need to be limited, the wide gear ratio difference isn't needed with 5-6 gears . Having the option to throttle and GO🤜, would be cool, if it could be managed, the ability to lock out the CVT variable drive ratios. Ot click into 4-5 gear and throttle and go! Anyway, a decent size engine, 440cc +, with expansion chambers. And a chambered muffler, kind of a cross between a muzzle supressor and a performance car muffler on a miniature scale. For a some what quirt engine, while maintaining flow. Possibly creating a low pressure to scavenge the cylinder, start by splitting a decent wall thickness of 2.5' tubing, possibly flatten it out a bit. To about 1.75-2.0" cut out bulkheads, for chamber walls, with. A hole 1/4 the distance from the top, saybits 2" x 4.35" tube the hole center being just over 1" from the top. With the exhaust tubing being approx. 3/4"-1" drill out the holes, use a press to dimple the holes . Creating sbout a 1/4" dimple so the hole flows with reduced eddy currents. Weld a 2" long piece of tube, that the expansion chamber will fit into. To one of the the plates. With the dimple being 1/2" larger than the hole. The exhaust inlet be ring welded into the dimple. Possibly make it a cone shape and bore out thr hole slightly. Weld in the exhaust tube plate to one side of the 2.5" (or 2"tubing) and align all the otherplates with the dimples pointed side about 1/8" from the flat of the next leaving about 5/8" to 3/4" from flat to flat of the plates. With the 2"-2.5" tubing being about 12"-16" long and the final plate having approximatelyg 1" tube with a slight recversed funnel shape to it, going from 1¹/⁸" to 1" as the outlet. The final 3" bring a chamber with a 5/8"-3/4" tube running from the chamber back to the inlet disc with 1/16" Holes drlled on 1/2" centers. Then fill the chambers with ceramic wool except for the last 3": chamber, the remaining half of the tubing, gets a series if 1/8" hole drilled where the plates fit ?to allow the plates to be plug welded to outside tubing. To keep the disc secure without rattles. The exhaust should flow freely, with reverse flow being very poor, it should flow as if it were a check valve. The final chamber should create a low pressure to scavenge the tube, the hole filled to tube should add a deep tone possibly add two additional 1/2" tubes. This also relives any pressure in the chambers. The aluminum material should should also keep the sound inside the muffler. The frame , built similar to the 70's street and trail. Only built from aluminum. With a modern mono shock in the rear, with a tubular swing arm. Fabbed from 1.75" tubing with super moto spoked rims powder coated a brass,/bronze color with black spokes. The forks matching. With a black frame. And with brass swingarm. Carbon fiber fenders, an aluminum fuel snd oil tsnk, with carbon fiber cover to simulate the fuel tank. And theseat being a flat cafe style with diamond tuck stitching, a micro fromt farring and headlight. With a pair of projector, with LED's and a center hi/low headlight the normal headlight being a running light, the high low projectors bring both bright or high beams. Running light / normal low beam ,then norml high beam. Then the added projectors being 160 watt leds in two colors daylight white, and ice blue white, the normal headlight having a amber hi/lo, and daylight white, with the switch allowing either normal headlight or projectors cant be off. But they can all be on. With a pair of small projector driving lights at the bottom of the frame. In amber to operate as fog lights and the whole backend of the seat and a 1" thick strip under tge fender being stop /tail and turndignals with the license plate mounting. On the swing arm under the muffler it bring just above the rims axel. The muffler outlet simulating a 1.75-2" outlet and quiet for a screaming 2T! Even a 440 would be awesome. Port it a bit, get about 2k rpm from it. Possibly add a supercharger and efi. Attempting to keep it the size of a 125-250 cc,with a much lower suspension the belly him height barely higher than a CBR, with 17"-18"rims and 240-260 rear rim 160 front. And gauges above the headlight and possibly clamp on's sory to ramble, i have had this in my mind soo long, im about ready to sell it and buy something else!😅, either a snow sled engine or a Ninja engine about 600 - 750cc no largervthan a 900, the 2 cylinder is the reason for ninja engines. Even a 250 ninja would be cool in a super moto style bike. A semi super moto meets a cafe bike. Something light and somewhat small but definitely not undersized or underpowered. What kind of power could a supercharged 440cc 2T EFI engine produce at .8-1 bar boost??😮. Have a great day!

[@Q.L.Engineering]

Good luck with your project.

[@petrdosel3137]

Hey i love your work is there a posibility that you would tune my engine? I will pay ofcourse😂

[@Q.L.Engineering]

Petr, please contact me via [e-mail] Regards S.v.S

[@motobiglove]

А вы не делаете тюнинг комплект шестерен для Явы 350 634?

[@Q.L.Engineering]

Not required for me. And a twin does less hammering per revolution, so the gear should last.

[@Adventurak]

Crazy 👌👌

[@Q.L.Engineering]

👌🏻👌🏻👍🏻☄️

[@pavelvincenc5314]

Keby takýto ľudia pracovali v jawa od začiatku, nemuseli by teraz made in china motory dávať a boli by jednotka na trhu. Skvelá práca od začiatku po koniec 👍👍👍

[@Q.L.Engineering]

I’m sure Czech JAWA people could deliver the same or better quality if they wanted to. But most customers wouldn’t want to pay the price they had to for home-land-made products.

[@Varela_mdv]

это просто нереально круто - привет из России

[@ExoRcisT.]

👍👍👍👍

[@Q.L.Engineering]

👋🏻👊🏼Thanks.

[@skmodificationsrajdhani9259]

Any gair box For sale price please gair

[@tymek6758]

what is its maximum speed?

[@Q.L.Engineering]

145-150 kmph with reso-pipes. 138 with stock pipes.

[@Einimas]

Oooo original škoda gear hobber, might be equipment that cut the original gears just the operators are more motivated. :D

[@Q.L.Engineering]

ŠMT (Škoda Machine Tools) still makes heavy duty machining equipment until today…

[@Einimas]

@@Q.L.Engineering love how the author improved weaker parts.

[@Q.L.Engineering]

Thank you Sir.

[@savitadhotre7525]

Like it

[@Q.L.Engineering]

😄👍🏻

[@John_heidinger]

Ostra 250 🤌

[@PeVeln]

Weren't you thinking about 5 speed gearbox?

[@Q.L.Engineering]

No.

[@alex_fbiblockstrike6411]

I think, that JAWA need 5 gearbox.

[@Q.L.Engineering]

Good idea Mate.

[@Fidlaa]

české ručičky v praxi

[@babkavakci]

Typek je nemec ale😂

[@SIMPL3_7495]

FİNALLY

[@Q.L.Engineering]

Haste makes waste, mate.

[@Mihu24]

The best on the corporations have 3% of your brain...

[@Q.L.Engineering]

That reads exaggerated, but thanks for watching.

[@Tobi08150]

was sagt der tüv dazu ? 🤔😂

[@Q.L.Engineering]

Nothing.

[@324td486]

Kto mi zrobi skrzynię do Pannonii?

[@Q.L.Engineering]

No, unfortunately not possible.