Jawa only idles w/ choke on.

1988 Jawa 210 2 speed all stock except for newly mounted sha 14/12 and an extra hole drilled out in the baffle.

It only idle with the choke on, and will not start w/o it. even warmed up.

Cleaned the gas tank, petcock, new fuel line, cleaned the carb extensively. tried a 52 jet, 54 jet, 56 jet.

new spark plug b6hs .5 mm Gap, new boot. has spark.

stock sha mesh air filter and cover.

Adjusted the timing to spec.

50:1 gas/oil ratio.

checked for air leaks.

tried every possible turn of the mixture screw.

Gonna go nuts fiddling with this machine. (edited)

Re: Jawa only idles w/ choke on.

sorry for being sideways and crappy quality - this is the bike idling, at 8 sec in i disengage the choke and finesse the throttle but it stalls out.


Re: Jawa only idles w/ choke on.

gently pulling throttle with the choke still on

Re: Jawa only idles w/ choke on.

Not completely ur prob, but ur gap is too big on plug...more like .028- .032...idk shit bout shas tho...

Re: Jawa only idles w/ choke on.

are you sure?

In the 210 workshop manual on jawamoped.com they specified a .5 gap for a PAL N7 R and ii have the equivalent (B6HS)

Re: Jawa only idles w/ choke on.

I have a 207 motor...tried the high gap...shortened it and its better...but I got that jackoff on there

Re: Jawa only idles w/ choke on.

Brent Bublitz /

Reel it all back.

The symptoms point to you running very lean. The only difference the choke makes is the density of the mix. Choke on, rich, choke off, lean.

You either have a blocked idle circuit, you are under-jetted or you have a massive air leak somewhere you have not checked yet. How have you been checking for air leaks? How sure are you that the carb is clean? did you run a wire through the idle circuit hole?

I had crappy idle after cleaning a 14:12 twice. I finally ran a chunk of wire through the idle passage and knocked a huge chunk of crap out.

Re: Jawa only idles w/ choke on.

I checked for air leaks by spraying carb cleaner around the carb, intake, head, and cylinder where surfaces meet. there was no change in RPMS.

Carb cleaner and compressed air inside carb. I'll try poking a wire around in the tiny passages nexttime.

to be clear , it idles and will run w/ the choke on just fine, but wont start/idle/run at all with it off.

idk if this matters but theres a giant air bubble in the gas line (its only a 6 inch tube from petcock to carb) and i have a full tank.

Re: Jawa only idles w/ choke on.

Wicked, i was talking .5 mm, if your talking inches that'd be .019, so youd set the gap a little larger then me at .7 or .8 mm which is .027 - .031

* edit to above post,, it idles and will run w/ the choke on just fine( fine meaning 10 mph and not stalling) (edited)

Re: Jawa only idles w/ choke on.

John Warren IhazJawas /

just a suggestion do you have the stock carb try putting that on tune it see if it will run and idle, then you can rule out if its the carb

Re: Jawa only idles w/ choke on.

you could try a richer throttle slide. Does your slide have a steep angle on the bottom? That would mean a lean idle mixture.

your crank seals may be bad also.

Re: Jawa only idles w/ choke on.

fallout Survivor /

crank seals leaking suspect.

Re: Jawa only idles w/ choke on.

W/ the Jikov last year it was able to idle and ride reguardless of choke position but still stalled after a few miles and wouldn't reach top speed. Would start right up again after a few seconds of pedaling.

Upon reassembly of the jikov for the nth time i smushed one of the sensitive brass float bubbles so i put it aside and bought a used Sha and a gasket kit.

Hope its not leaky crank seals.. but that's the only thing i've left untouched and are probably 25 years old. looks like i may haveto put in an order overseas..

Can they be replaced without taking apart the engine? If not it maybe wise to check if i need anything else, bearings, rings, etc too if necessary because ship time is 3-5 weeks. Did anyone hear that pinging in video 1? it does that at idle and more noticeably when speeding up near second gear. it's like BB flying around inside going ting ting ting.

Re: Jawa only idles w/ choke on.

found a site that carries all of the needed seals, are they the right type though?


Re: Jawa only idles w/ choke on.

Theres 4 styles available on this site which are narrated by the dimensions( the 15 x 24 x 7 only comes in 827N). in the Workshop manual the Sealing rings in engine are unspecific of the style.

-Narrow Width

-822N Ground metal O.D,

-824N ground metal O.D Closed,

-827N rubber O.D.

17 x 28 x 7 -1 pc

15 x 24 x 7 -2 pcs

22 x 32 x 7 -1 pc

35 x 47 x 7 -1 pc

28 x 38 x 7 -1 pc

Re: Jawa only idles w/ choke on.

yup those seals should work. Just get the style that's in your motor. They're probably the rubber od style.

I would do a leakdown test to see if they're bad first.

Re: Jawa only idles w/ choke on.

Theres atleast one seal leaking on the transmission side because theres new oil seeping in behind the clutches i recently cleaned and replaced. Gonna check the rest tmw. dodged a shipping delay bullet for now.

if replacing these seals doesnt do it its gotta be that damn thyristor because i was having these symptoms a year ago too with the same setup except stock carb. i tried making a homemade one from the wiki but it couldnt wire up right and refit the old hungarian unit (edited)

Re: Jawa only idles w/ choke on.

seriously noone suggesting just upjetting? I swear to god this has to be the carb, you put a 14:12 on and didnt jet it. you need a bigger jet. end of story. plug gaps dont enter into it. don't go assuming there are seal leaks because it's lean. if you haven't upjetted it's gonna be lean no matter what. 52-56 is not a wide enough range to say OK yea it's not the jetting...

leaky seal sucks, if you can see oil coming outta the crank seal, that's a good indicator that it is leaking. there's a rebuild with pics in the wiki


I've had great success making the thyristors, i think I still have one that I made which I could send you too. email me if you want it.

Re: Jawa only idles w/ choke on.

I replaced the leaky seals, that wasn't the main problem...

thing was the Petcock was clogged to hell. tore it open and rebuilt it. Bike will run and not stall if i hold the gas open a little at stop signs. that could be the loose throttle cable. other then that made 34 flat land and 37 downhill but i gotta put the new tire on before i keep pushing it. Pumped ..

Jawa Lives!

drill through 2 rivets, unscrew on either side of the petcock, pry out old rubber dohickey, throw the metal bits in some carb cleaner, cut a new gasket, screw it up and good to go


Re: Jawa only idles w/ choke on.

John Warren IhazJawas /

you should be able to tune the carb to keep it from staling now

Re: Jawa only idles w/ choke on.

yea definitely. except..the seals started leaking tranny fluid. figure out we pushed them in too far past flush w/ the case, oops. i learned something, search, research, then work on yer ped.

i appreciate the advice everyone, thanks. (edited)

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