Seems I have a problem with idle.

So, the 750 that got me here.

Braks rebuilt front and rear, carbs rebuilt, floats set, valves clearanced. Should need a sync and be good to go, right?

So I build a synchronizer and go at it. Synched 1-2, then 3-4, then 1-2-3-4.

And then it revs to 3000 all on it's own. And when it doesn't and runs at 100 or so, there is this clattering sound from the engine.

The only thing I can think of is that the timing chain guide gave up the ghost and the chain is loose.

What else could it be?

This is disappointing enough to think about dumping this bike...

 

Re: Seems I have a problem.

probably just the cam chain slapping around with poor running/jerky engine. Your description of the problem was quite vague. Can you hit us again with a more detailled description of how its running/starting etc?

 

Re: Seems I have a problem.

what do you mean runs at 100 or so? Do you mean 1000rpms?

Are your vacuum rubber caps new? They can seem good but still leak and after getting pried off and on that might crop up. Drink a brew, sit it out for a bit. Whatever it is can't be that hard and can be solved.

Also just to be clear, how was it running before the synch? Or do you just now have it back running after all the maintenance?

 

Re: Seems I have a problem.

Probably a vacuum leak, either between an intake manifold and the head, or throttle shaft seals (unless you already replaced them.)

Or you missed on either the sync or float levels.

 

Re: Seems I have a problem.

Dont worry,
The xj sound notoriously crappy and jerky when its running at a low rpm
Im not sure if it has to do with the starter clutch or the transmission.

try spraying starter fluid or better yet an unlit propane torch around the intake boots to check for a leak.

Did you use the YICS tool when you synced and colortuned?

 

Re: Seems I have a problem.

Huh? :? are your carbs synced up properly?

 

Re: Seems I have a problem.

Only time my Maxim-X ran crappy and jerky at idle was when the carbs were out of balance (out of synch).

 

Re: Seems I have a problem.

I agree. My 550 when I first got it was noisy at idle-but after a valve adjustment, full carb clean, synch, once through the maintenance schedule and several oil changes with Q moto oil it now sounds like a well oiled machine even at idle. Of course it's not as quiet as a modern water cooled bike, but that would be scary if it was.

In short the XJ's may produce more decibels of sound at idle than some other similar bikes, but they should sound rhythmic and healthy all the same.

 

Re: Seems I have a problem.

Sonofa...

One of the rubber sections of the YICS tool was ripped up. I guess this makes the sync completely wrong.

 

Re: Seems I have a problem.

Yeah, would mean the valves were more than fag-paper tight :?

And yep afraid it's true JPaganel, sync is likely out if the YICS tool wasn't sealing correctly. At least it's an easier fix than a timing chain

 

Re: Seems I have a problem.

Time to use the YICS rag doll! lol!

 

Re: Seems I have a problem.

^^ +1

Or shopping for silicone hose of the right size that doesn't come from a pothead shop lol

 

Re: Seems I have a problem.

I don't use a YICS tool......yes, I have one--it's in the plastic sleeve that it came in. It's the fancy one, too. I like it--it looks neat and I can show people one at carb clinics.

dave fox

 

Re: Seems I have a problem.

YICS tool use is stressful, i always wind up destroying the little rubbers on the tool. I just stuff oiled up rags in and can leave it there the whole time, not worrying if it burns or gets a little warm .

Good luck with the sync!

 

Re: Seems I have a problem.

don't use the tool and live happily ever after

 

Re: Seems I have a problem.

Aaaand...

@#$%^&*()_)(*&^%$#$%^&*()_)_+_+_&$$#@@$%^&*&*&^#@#!#@#!!!!!!!!

Redid the sync with the tool sealing correctly. It idled at 1000.

Let it cool down, pulled the tool. Put the plugs back in. Put the tank on.

With enrichment completely shut off it promptly started and idled at a nice 6000 RPM. Fdisk me sideways.

I guess what upsets me is that I had such high expectations...


BTw, to answer some of the questions, vacuum caps are new, throttle seals are new, MNMaxims helped me with float levels. Intake boots are not cracked or weathered in any way and are bolted up tightly.

I wonder if YICS tool making a difference means that there is something wrong with the head.

 

Re: Seems I have a problem.

Are your copper sealing washers on the YICS plugs in good shape? (are they missing even?)

Sounds like you have a HUGE leak somewhere... or your throttle cable is hanging up somehow & pulling your leg...

 

Re: Seems I have a problem.

Washers are OK.

The leak has to be truly something. Pulling off a vacuum cap doesn't make any difference...

 

Re: Seems I have a problem.

you're sure the throttle is closing properly too? Many people have been fooled by either a frayed cable or bad routing under the tank before now, myself included.

EDIT-: and I trust your carb pistons clunk test nicely too?

 

Re: Seems I have a problem.

Is that possible one or two YICS passages are plugged up?