Air fuel mix

[Fizzyhair]

I've only ever had to do this on a single cylinder bike or car so I'm after a little help.

I need to get the bike to a garage to get my carbs balanced (did it myself but I don't trust my gagues tbh they were cheep)

However some cylinders are running rich which is causing lots of spluttering and some very sooty plugs. What is the proper procedure for setting air fuel on a gs650 and where on the carb do I make this adjustment on the gs?

It's not got to be spot on as the garage will double check it. (engine sounds fine idling and up to 2000rpm.

[Fizzyhair]

I can't seem to get this right lol. Is there a good guide to doing this somewhere?

I've made sure everything is airtight, cleaned everything and replaced plugs etc. New seals the works.

Just running rich and I'm looking for a nudge in the right direction. Thanks everybody.

[hampshirehog]

The only adjustment you have as standard on those carbs is the via the mixture screws. In = leaner, out = richer. You did take them out when you cleaned the carbs I suppose?

[chef1366]

adjust the valves too
Did you take the carbs apart and clean them?

[Fizzyhair]

Gotta love a sarcastic answer lol. I meant is there any order to do them in. What is the correct procedure? Should the engine be hot or cold etc I'm just wondering really if there being four carbs makes any difference to the way I do it.

Never mind I'll work it out

[chef1366]

Who's being sarcastic?
Check Bascliff's website. There is a tutorial on how to do a proper Sychronize.
If your valves aren't adjusted poperly you won't get a proper sync and your bike will never run right.
I was just asking.

[hampshirehog]

Me neither - I wasn't taking the wotsit. If you haven't completely stripped the carbs down to basic components and thoroughly cleaned everything (and I really do mean thoroughly) you could well be fighting an uphill battle. Many have tried half measures and all have failed.

You adjust each mixture screw in or out until you hear the highest revs. About 2-3 turns out gives you a good starting point and adjust steadily as you listen (the engine will run slightly behind you adjusting).

Plus ditto Chef on the valve clearances. REALLY important task - the bogeyman will get your engine if the valve clearances aren't correct (and 1000s were never checked).

All carb adjustments are done with the engine at normal operating temperature (hot) and it doesn't matter which carb you adjust first - though you need to synch against #3 as there is no adjuster on that carb.

[BassCliff]

Hi,

The idle mixture screw, seen below, affects only the idle mixture. After you start rolling on the throttle, then other carb circuits come into play.



Is your air filter clean and very lightly oiled? Do you have good spark on all four cylinders? Are the carbs properly cleaned? Have you changed the jetting? Is the petcock in good working order?

Here's what I'd do:

1. Clean the carbs properly and reassemble with new O-ring kit.
2. Bench sync.
3. Set the idle mixture screws about 2.5-3 turns out.
4. Vacuum sync.
5. Adjust idle mixture screws using "highest idle method".

This is assuming stock everything; jets, airbox, exhaust, etc. You'll find more information on my little website. Start with the READ ME file. It contains a couple of lists of all the critical maintenance items that must be looked after. Any shortcuts will leave you stranded on the side of the road.


Thank you for your indulgence,

BassCliff

[hampshirehog]

Hi,

The idle mixture screw, seen below, affects only the idle mixture. After you start rolling on the throttle, then other carb circuits come into play.

Good photo from Cliff showing you where the mixture screws are. Yours will look slightly different as the photo is of a US bike but they will be in the same place and work the same way.

Although Cliff is right about those screws only affecting the idle circuit you need to be aware that you will be riding on that circuit quite a bit if you are keeping to the speed limit. It doesn't just control tickover.

[Fizzyhair]

I've actually done all of those things except valve clearance checked but that's why I'm heading to a garage. The main issue is I can't ride it to a garage to get it checked because it's got no mot and it cant get an Mot untill it's working.

Original jets still in place, original airbox and lightly oild filter. The stock original exhaust had a big ass hole in it and the original owner set the fuel mixture to richen it up to compensate for the extra air drawn. (I know what a stupid idea but it worked) my new exhaust is not drawing the same air flow and all of a sudden the plugs are very sooty. I followed the carb guide on this site for my carb clean.

The new exhaust is a motad 4-1 btw as it's all that was available really at the time. The minute revs are applied it splutters. So not great but it actually idles wonderfully. So I'm thinking maybe somethings blocking a jet on one carb?

Thankyou everyone

[cowboyup3371]

Tell me again why you are taking it to a shop to do? They will only fleece you for your money, possibly ruin your bike, or at the very least get it back in worst shape then when you took it in. How far from Hampshirehog are you? I know he already posted here but at least ring him up and I'm sure he'd walk you through things.

[Fizzyhair]

I'm not confident to set the clearances yet. I'm still teaching myself. The head still has me a little unsure.

[cowboyup3371]

Fizzyhair, trust yourself. I didn't know anything about doing that stuff either and you know what, IT'S EASY. Follow the guide on Basscliff's site, talk to Steve when he posts for his spreadsheet, and dive in. There's nothing you can do to break it that you cannot fix afterwards. This is my first motorcycle too and although I rebuilt a car engine before, it had been awhile. I was deathly afraid of doing much and still am for some things as I'm more of a hands-on learner. But, posting questions and taking pictures will go along way for you.

Do you have a digital camera? If not, get one and just flood your computer with pictures. Just remember to refer back to them when it's time to put things back if you forget.

[Steve]

Plus ditto Chef on the valve clearances. REALLY important task - the bogeyman will get your engine if the valve clearances aren't correct (and 1000s were never checked).

I've actually done all of those things except valve clearance checked ...

Valve adjustment is CRITICAL.

And don't wait for them to get noisy before you address them, either, as they will tighten up, not loosen.

Tight valves will burn, if you can get the engine started in the first place. (Tight valves will make it very hard to start when cold.)
For a bit of help, read my sig, join the several hundred that have received my spreadsheet. (518 users, so far.)

Just a small example: I adjusted the valves this past week on my '80 850. I have had the bike for only a year, and have managed to put about 5,000 miles on it. I have it here in New York, while I am working here. My wife came to visit for a week, we are going on a 1000-mile (or so) trip this weekend. She brought my shims so I could check the valves.

Of the eight valves, one was just beyond the max clearance, two were pretty good, FIVE of them were too tight to pass a .0015" feeler gauge (yes, I use INCH feelers ). I shuffled the appropriate shims, checked the clearances again, and TWO of them were still too tight. Had to drop one more shim size on them.

The bike had been running just fine, even starting fine. Probably because the three valves that were not tight were all intakes. My valves are now set, the carb sync was close enough that I chose to not mess with it, I am ready to go.

Headed off to bed now, the alarm will sound in about 6 hours.

.

[Fizzyhair]

Well if if I can get an mot on this bike I'll be able to actually test it propery. My main problem is that I don't drive I only have a bike. My other bike (zx9r) was run into by a lorry in a car park and destroyed last month, and their insurer hasn't coughed up yet as it seems he was disqualified. So I need to run this bike fairly soon to get to work. So it's got to be a a garage for speed.

I do almost everything myself on my bikes with the exception of the valves which i will learn. Thanks for the help I'll email you for that sheet. For now I use a guy who used to race bikes who's got a small setup a few miles down the county not a mainstream garage chain. He's very good. It dosnt help that most of my project bikes have been vintage 2strokes.