Mikuni bs34s - bike won't start

hello all. i'm very frustrated with my '81 kz1000 ltd. actually, it's the carbs. the bike has been sitting for almost 2 years. it ran, rough, before parking it (had uni pod air filters). i unrestricted the kerker 4-1 baffle and i'm using emgo air filter pods - oiled. i just installed the correct dynojet kit to spec. before the dynojet, i couldn't start the bike without squirting gas into the carbs first and need the choke all the way out. it runs rough and only at high rpms. will not idle. i pulled the air pods and noticed that if i hold my forearm against the carb inlets it will start. i know dynojet does not affect starting or idle circuits. i did inspect the carbs before attempting to start it. internals looked clean and no gunk and the boots were replaced and look good. so, it's gotta be in the idle or starting circuit, right? i have the factory service manual. i am stumped and if anyone can offer assistance, it would be greatly appreciated.

thanks in advance, Mike

I'd bet on clogged low speed jets. They are really tiny and plug easily, especially with the c**p they sell for gasoline these days. Sitting for as little as three weeks can lead to this problem as the fuel begins to fossilize.

thanks for the get back TKZ

update time. pulled the carbs, cleaned 'em (3 times!), fitted the dynojet kit to spec, checked the reed valves, oiled the emgo air pods and replaced some vacuum hoses. starts okay and now it'll idle. problem now, when i'm riding, it races up in rpms when i roll off the throttle and clutch to shift. it's worse when i'm exiting the highway - the rpms really races up when downshifting and takes a few moments to settle down. throttle cable is good and snaps closed with the return springs on the carbs. just picked up some hose for the carb sync and still need to balance, although i eyed 'em close as per the service manual.

again, any help would be greatly appreciated.

Mike

Since you seem to have eliminated the throttle cable as a culprit, I'd look very carefully for vacuum leaks. With the engine idling, carefully spray some brake cleaner (some use wd40, but I think it is way too messy)around where each manifold (carb holder) mates with the head and also where they mate with the carbs. If any of them have cracks, automatically suspect them. Also look carefully at the little plugs that go over the synch tubes. Also inspect the line to the petcock. A small leak in any of these places can mess with the way the engine runs and drive you mad............. :silly: :S

High idle is symptomatic of air leaks as noted above

I'd replace the boots and O rings, not cheap, but at least you know they're good


Also, the CV carbs need a fair bit of restriction on the intake side to attain proper vacuum. You might need some higher quality pods from APE or K&N. Also, put some packing back in the exhaust and get some back pressure there

Do not oil those air filters. Roy

thanks for the replies.

latest update:

removed the pcv cannister, connected the reed valves via hose and plugged the small vacuum hose to the carbs. no change - still over revs.

pulled the carbs once again and inspected the float heights (all to spec), cleaned the jet needle (again), checked the slides, refit the carbs. problem stopped. was able to start, idle, roll the throttle, low speed tested, highway tested. seems normal.

yesterday, took a ride and the problem returned. rpms rise and over revs. very disappointed!

seems the slides are hanging up. cannot think of any other reason. will try to recreate the issue in the garage. any suggestion on cleaning the slides other than carb cleaner? they are all really clean looking save for some light brownish discoloration.

thanks in advance, Mike

update:

removed the carbs and inspected all hoses, re-cleaned the slides, re-checked the pilot settings, jet needle and more. when i re-mounted the carbs and throttle cable, i twisted the grip and although it snapped back, i noticed the sprigs on the carb weren't snapping back as quickly or evenly each time - almost lagging ever other twist. took out the can of wd40 and lubed up the springs. seems to have cleared up the issue.

not going to call the issue resolved until a few more runs.

emboldened by my apparent success, i'm going to tear into the Keihn carbs on my '85 ZL900 Eliminator. they have never been cleaned and i think it's high time i got to it.

again, thanks for all the replies and suggestions.

regards,

mike

good for you! nice bikes BTW. I had a weird issue with my carbs when I first put them on, I was thinking it was this and that, and it turned out to be the throttle cable like yours...it's always the last place you look isn't it

Nice Eliminator Post up some pictures if you get a chance.

When you take the tops off the carbs, look to see if the diaphragms are twisted. If they are, you'll spot it straight away.

I have a 1000 with bs 34s. I sugjest putting the baffle back in. my bike will not pick up speed or run correctly. without the baffle.