Carb Question

I notice while syncing my carbs that when I put pressure on the screw ( pushing throttle rail down) the bike lowers it revs. The throttle cable has plenty of slack.

Could this be the springs getting weak? Any ideas?

 

weak or not moving freely, i have thought about adding an extra spring at the cable's end.

 

After sync I had the hard start problem so I pulled the carbs and cleaned the enrichment circuit. Fixed the start problem. While I had it off and hit the throttle rail with wd40. works nice and smooth but still the bike will rev down when you press the rail.

Carbs have been cleaned, floats set etc. I synced using Ricks stuff the yics with marvel soaked tshirt pieces and a home made tube type manometer. (works but it's a pain - I'm gonna get a yics tool and a vacuum gage). I got everything to sync and even double checked. Then I removed the yics stuffing and colortuned.

The question - why does the idle still sit and around 1200 (idle screw al the way out).?

 

something is holding the butterflys open.

 

The question - why does the idle still sit and around 1200 (idle screw al the way out).?[/quote]


Leaky throttle shaft seals? I did mine and idle improved a lot.

 

Yea my thought too but they sure look "closed" when I have the carbs off. I can see some light around them near the bottom but they all look that way. Not held open but like they don't fit exactly. I had been assuming this was normal...


Conn110 - that is a good thought - is there a way to test prior to replacing the seals?

I have new vacuum plugs to replace mine justi n case it's leaking there.

Seems I place orders with Chacal weekly as I find things - wish I could figure out all I need and save some shipping

 

What did you use to Bench Sync the Carbs.

Anything round will leave the Throttle Plates too open and cause the rev's to be increased rather than having the Throttles closed.

Pull the Carbs and do the Bench Sync over.
Use quarter-inch wide strips of Business Card.
That will allow you to have the throttles closed and bring down the Idle.

Be sure to lube the Throttle Shafts where they pivot in each body.
Marvel Mystery Oil in the Shave Pivots will lube them and condition the seals.

 

I used a feeler gage. But I'm curious. When you bench sync you are holding 3 open and matching the others as close as possible. So as I understand it they will then all close and open the "same".

Once you do the "live" sync those settings are all changed (tweaked) to match 3 which is closed at idle. Right?


I thought bench sync only got u close for the real sync - what am I missing?

Thanks

 

Having the Throttle Plate on Number-3 being nearly closed so that the other three Throttle Plates are nearly closed at the beginning.

Then, you can control the Idle with the Idle Adjustment Rod ... and when the Adjustment Rod is backed-off where it contacts the linkage ... the Throttles are actually closed shut ... requiring you to add a turn or two in order to get the revs up.

 

Sorry thick headed here - 3 is not adjustable except by idle screw correct?

 

Correct.

Three is the BASE Throttle used for Sync.

4 is set to match 3

1 & 2 are matched by adjusting 1 -to- 2

2 is matched to 3 bringing along the 1 Carb as they are married.

 

Ok that is as I understood it.

Since I have "live" synced the carbs how would re bench syncing help? I am going to re live sync to be sure they are correct.

I would rebench sync if I can understand why ( a real pain to pull and reinstall carbs as you know). It seems it is a starting point that I have passed?

Sorry, I'm not doubting your expert advice just trying to understand...

 

If you already LIVE Synced ... You don't have to go Back.

You must be getting some Air introduced to the Intake that keeping your Idle raised.

 

OK cool thanks for your patience. I used a home made tube manometer but I have purchased a vacuum gage and fabed restricter per your excellent instructions. YICS tool coming for chacal (I used your stuff method).

So when I resync it should be more accurate although I thought I had it right. If that isn't it maybe its the seals. Boots are fine.

 

bill, you said you can close the throttle by applying pressure, so you know what the problem is, so you should be able to fix it.

 

Working on it Right now I'm suspecting my sync is very close but not correct. I believe my butterflys close just fine (not hung etc).

Thanks for all your help!

 

Update - I have a proper YICS tool and a vacuum gage but even when I get the vacuum even I still have high idle.

Only conclusion is the throttle seals are toast. Examination of the outer seals does show one in bad shape. Funny thing is Marvel oil on the seals does not change things.

So anyway yet another order to chacal and a complete rebuild in two weeks (wont be able to do it next week).

 

Well Wizard I found the problem with the throttle rail not closing in my rebuild of the carbs. The main spring was not hooked in the right spot so did not pull the throttle down completely.

For the rest I replaced all the seals, needles and floats, recleaned everything and did a bench sync. What a difference. I still need to do the vacuum sync but I have the idle down to 1100-1200 when hot vs 1500-2000 and pressing the rail no longer makes any difference. (yeah)

Now I can get down to tuning. She already sounds and reacts different (better) to the throttle. Much snappier response.

 

Did you do the following when you did your Carbs?

1. Emulsion Tubes. Complete?
2. Fuel Bowl Starter Jets?

3. Refinish the Diaphragm Piston Bores?

If you think its running good after a Carb Cleaning and you haven't done any Fine-tuning ... yet ... we'll all get the Big Mo-Jo Woikin' ann tune dat baby up!

 

Hi Rick I owe you a BIG thanks. I did it ALL based on your instructions. I had done a good cleaning before including the items you list but I went ahead and cleaned the carb bodies using the pinesol method. Then soaked the brass bits in carb cleaner. I have the poke tools from Chacal so I poked every hole and blew cleaner through them (including the pesky starter jets). Shined the piston bores like mirrors, replaced all the rubber seals and o-rings. Replaced the needles and seats. Did the bench sync using business card as you suggested.

Today I did the sync using a vacuum gauge and your old school method. About 4 rounds through the carbs tweaking and I had them balanced. Bike Idles great at 1000 or so (who can tell 1050 on that tack ).

I did not get a chance for a long ride but a quick trip up the road and she seems to be doing great. I have to do another colortune then start reading my plugs to dial it in.

Thanks to all for the advice and the great how tos on the site.