idle difficulties

so i've rebuilt the fuel delivery system (rebuilt petcock, float bowl gaskets, needles, and valves). the bike is no longer leaking like the exxon-valdez. now the next step is getting the idle right.

started her up today, had some difficulty starting but got her going. played with the idle screw till i got her leveled out at around 1200. shut off. turn over again. idle immediately spikes to over 2000, sits for a second or two, then comes back down to around 1200. checked this a couple of times, and then took her around the block.

almost immediately, she's jumping up to 3000, then 4000. seriously over-revving the engine when i take her down to first and second, so put her in third and just sit back to let her cruise to home base.

whenever i would brake to stop, she would slowly start revving down. very slowly - but the moment i engaged the clutch, i could feel the power immediately falling off and she would start edging towards a stall.

thoughts? comments? any tips or ideas would be mucho appreciated.

ps - i know i should probably be doing my own colortune and synch, but i feel this is outside of my abilities and just want to get the bike to run ragged but well enough to take it to a shop i know about 20 miles distant to have the carb synching done there.

 

Idle rising could be a throttle cable issue. Check to make sure this isn't the problem by turning the headstock full lock left/right at idle and see if the RPM changes. Other than that I would suspect an induction leak. Spray the flexible boots between the carb and the head with WD-40 and see if the idle changes. Don't use starting fluid! I've heard of some nasty little fires started this way. If neither of these two things have any effect, I would suggest yanking the carbs and giving them a good going through, looking for leaky needles and seats, loose jets, plugged pilot jets, leaking enrichener valves, or excessively high float levels.

 

As CapnKirk states, check for air leaks. If none then your problem may simply be that the sync and colourtune is all that's needed to fix the reving issue. Particularly if starting is an issue.

To be honest if you have rebuilt everything in your fuel delivery system then I doubt a sync is outside your abilities. Do a search of the forums on "Manometer" and have a read. there are some very cheap homemade carbsyncing tools that will get your sync in the ball park if not perfect.

A search on "Bench sync" for the carbs will also bring up some worthy reading.

Hope this helps
HG

 

I have to agree with the SYNC, while performing this on some other bikes you have an idle rise when adjustments are made to carbs. It sounds like the carbs are out of sync, one or more is getting more air/fuel mixture than others and raising the idle of the bike. The carbs try to compensate for this added mixture to one cylinder which in turn raises the idle upward in a chase to catch up.

 

Can anyone put up a picture of the idle adjustment screw (?) for these bikes? It may show it in my Haynes manual, but as of yet, I can't seem to find it. I have to assume that you can adjust the carbs with the bike still together since it seems like most people do the adjustments while the bike is running.

 

the idle adjustment screw is the big round knob between carbs 2 & 3. you want to adjust it while the bike is idling and the choke is closed.

as for synching...

i can see that hooking up a manometer to the boots looks pretty straightforward, but i'm not entirely sure on how to adjust the air flow to get them synched. i'll look futher in the forums as suggested.

thanks very much guys. always appreciate the responses around here - otherwise, i'd never figure out how to get this bike back into primo running condition!

 

There are 3 Synchronizing Screws on the Carb Linkage.

One, Two and Four are adjustable.

Three is FIXED ... and, is the carb which 1, 2 and 4 are ultimately synchronized; too.

Begin by Synchronizing the No.-1 Carb -- to -- No.-2 ... by adjusting No.-1's screw until they're in sync.

Then, Sync the No.-4 Carb -- to -- No.-3 ... by adjusting No.-4's screw until 3 & 4 are matched.

Finally: Adjust No.-2 -- to -- No.-3 and you've got 'em Sync'd!

 

are the screws the ones that are going through the body / rod and are connected to the choke? when i took the carbs off, i replaced three of the screws, but the screw on carb 1 broke off and so i left it. if these are the screws you are describing, i take it i'm gonna have to take the carbs off and figure out a way to get carb 1 screw out with a new one in and then start seeing about synching, yes?

 

zamboya, here's a picture of one of the screws you're looking for. (The carbs are off the bike in this picture.)

It's not on top with the "choke" rod, it's about midway and is part of the throttle linkage.

 

damn. i was screwing around earlier tonight with those damn little screws through the body. i think i spent a good two hours cursing rather vehemently the engineers who designed the carbs. ok - object lesson for everyone perusing this topic - buy the xjcd and NOT the factory manual scan off ebay. the factory manual doesn't have anything in it about tuning the carbs.

big thanks nick. very big.

 

Try this link
http://members.tripod.com/dave_jack/id38.htm

I' m not trying to send people elsewhere but because of time and my need to get out the door to work I'm sending you there to start.

I've found some really detailed articles on tuning these bikes but I dont have time to look now!

Sorry again

MIke