finishing the 850, carb advise (jetting) please.

[LW_Icarus]

OK, the engine is back together, wiring is done, exhaust and airbox have been repaired, got a new suzuki air filter complete, cuz I didnt feel like futzing with the seal on top, petcock has been replaced, new OEM intake boots, etc.

so I got it fired up yesterday, and it sounds good, no weird noises, no leaks, but it only runs on choke. will not accelerate, feels like fuel starvation, wont free rev at all.

I pulled the carbs back off and they appeared pretty clean. I went ahead and used carb cleaner in all the passages, and followed with some compressed air. I also removed the epa plugs over the idle mix screws, and increased to a 117.5 main jet over the stockers, which apparently are 115s , at least thats what I took out.

am I headed in the right direction here? it seems to me as lean as these bikes are, that one step up on the main is a good idea, I think the unsealed sides on the airbox probably caused the bike to fall on its face, after reading here, that also will get fixed tomorrow.

I guess Im just looking for anything I may wanna look at, my goal is to get a ride in by monday, and if someone can give any ideas/experiences that may help it would be greatly appreciated.

 

[SqDancerLynn1]

The air box needs to be air tight NO missing seals or covers

 

[KEITH KRAUSE]

Fix all airbox seals first and test.
The way you describe testing, after "firing it up, won't accelerate/won't rev free at all", would not involve the main jet. A step up on the main will not cause major problems if it was running correctly before the change, but I wouldn't have changed the mains.
If you're saying the bike will start and idle but only with choke, then this suggests a dirty pilot circuit and/or a carb vacuum synch is needed.
If the bike will not rev at all, won't accept any throttle above idle, then that suggests a bad diaphragm(s).

 

[LW_Icarus]

appreciate the responses, and heres an update- I have the airbox side seals fixed, and completely assembled the bike,tight and right.

it fires right up, sounds pretty good on choke. will not idle off choke. I did however go ahead and take it around the block, and as long as the choke is in the right place it runs decent down low, about 20% on with the choke.

it runs like a striped ass ape above 3500 rpm or so. very smooth, very quick. choke can be off, still accelerates fine.

I understand what you mean about not changing the mains without it already being tuned, but I had em, and had the bowls off, I wasnt so much thinking it would magically fix my idle problem though

I presume my idle circuit is foobed, I pulled one diaghram, it looked good, I need a long set of e-clip pliers to shim up the needle a little. again not gonna fix the idle but may be useful for future reference.

is there anything I can do short of dipping the carbs to clear the idle circuit? I think this is my last hurdle, and Im anxious to get on the road, I checked that I was charging and that seems good, and all else checked out.

I plan on getting the valves adjusted and carbs synched, but Im hoping to get it to idle even poorly, enough that I can ride it into the shop.right now Im not sure an 8 mile ride should be attempted.

 

[KEITH KRAUSE]

First of all, I don't know why you would want to shim up the jet needle on a stock motor. Your problem is obviously while running on the pilot circuit, not the needle circuit.
Since you can ride the bike, it's obvious the bike accepts throttle, so the diaphragms should be fine.
If the bike has to have choke to idle and to ride around at low speeds/small throttle openings, then the choke circuit being used is compensating for poor fuel flow in the pilot circuit. However, it's also possible a poor carb synch is the problem.
I don't cut corners when doing carb work. I do a complete job. But if you're really pressed for time, I'd first try the carb synch, at least a bench synch. No vacuum tool needed for that. Then re-test. If it works, vacuum synch as soon as you can.
If the synch doesn't help and you're sure you did it correctly, then the carbs must be completely cleaned and inspected.
By the way, do you notice the idle rpm's rising quite a bit as the bike becomes fully warmed up, or does it idle the same rpm cold or hot?

 

[Anonymous]

By the way, do you notice the idle rpm's rising quite a bit as the bike becomes fully warmed up, or does it idle the same rpm cold or hot?

My 1100's idle seems to raise slightly when warm. As I stop at a stop sign it takes a moment for the idle to drop to normal. Does this indicate a sync problem?

 

[LW_Icarus]

Idle is the same cold and hot, no real difference. at least as far as I can tell with it not idling off choke.

Im not really into corner cutting myself, but I have very little riding weather left in ohio, and a budget thats been blown wide open, so if clearing the idle circuit will get it going, Ill worry about a class "A" carb rebuild this winter.if I can't, the project goes on hold for a few weeks while I replenish the savings. the carbs are very clean inside, no sign of weather damage, and minimal varnish.

the only reason I was thinking raising the needle on a stock bike might be a good idea, is because these bikes are jetted so lean to begin with.seemed to me that getting off the ragged edge of lean would help. if it isn't going to be any help Id just as soon not fool with it anyway.

Ill pull the carbs back off, see if I can make sure the pilot circuit is clear, and bench synch the carbs. I appreciate your help, and will update a little later today as to what results I get.

 

[KEITH KRAUSE]

By the way, do you notice the idle rpm's rising quite a bit as the bike becomes fully warmed up, or does it idle the same rpm cold or hot?

My 1100's idle seems to raise slightly when warm. As I stop at a stop sign it takes a moment for the idle to drop to normal. Does this indicate a sync problem?

I consider 100 or maybe 200 rpm gain once fully warmed up as normal. A lot depends on changing outside conditions too.
A poor vacuum synch can cause all kinds of idle problems. If the cylinders are burning different mixtures or different amounts of mixture, combustion will be different at each cylinder. This uneven combustion can cause the "idle" to hang momentarily.
Another cause of a hanging idle is a lean mixture. Lean mixtures burn unevenly during the 4 stroke cycle. Not only will the cylinders burn uneven/out of time when compared to each other, but each cylinder itself will burn the mixture unevenly/at the wrong time.
Once in a while, a hanging idle can be a tight/worn throttle cable/linkage that's giving an intermittent problem. Be sure the cable is routed correctly and has the factory suggested slack in it.
If the cable's good, I'd hook up a synch tool and check the vacuum levels. Adjust if needed and test.
If you still have a problem, maybe an additional 1/2 turn out on your mixture screws will richen it up right. Maybe your screws are way off and need further adjustment? I don't know what's been done to your bike to suggest anything more.

 

[Anonymous]

Thank you, and sorry for butting in on your thread LW_Icarus!

 

[LW_Icarus]

hey no sweat Floydechoes, I am guilty of doing the same to others its all good.

OK, another update- I recleaned the passages, and bench synched the carbs. MUCH better now. idles without choke, albeit a lil roughly. doesnt drop down to a low idle right away. Im thinking tomorrow Im gonna try to get it in the shop and have the carbs synched/valves adjusted and screw a new set of plugs in it. its a lil rough at higher rpms now, Im blaming carb synch on that too I think.

I rode it around for about a half hour today, and it didn't act up otherwise. looks like Ill get to do some riding this fall after all

thanks again!

 

[KEITH KRAUSE]

Glad to hear it's running better. Hopefully the mechanic will do a really good vacuum synch. It's smart to adjust the valve clearances before the synch. Also be sure the timing/advance timing is correct before the synch. Let us know how it goes.

 

[KEITH KRAUSE]

By the way, I forgot to ask earlier. You said you removed the tamper caps over the mixture screws. Did you adjust them at all? If the caps look like they were on since the factory, I wouldn't change their settings. But if you took the screws out for cleaning and didn't count how many turns out they were, you could have re-set them too lean? Or, maybe you just turned them in some?
Each bike varies some, but they are usually about 2 turns out.

 

[LW_Icarus]

well, when I removed the tamper proof screws, I did indeed tamper. screws were removed , and replaced , they were about 2 1/2 turns out earlier, 2 turns out now as thats the closest thing to a baseline before I read your reply.

is there a such thing as a carb "upgrade"? meaning is there a later model carb I should be keeping my eyes open for, or should I just live with these and think about replacing all the wearable parts? I think I figured near 200 bucks in pieces parts not counting the diaphragms. and those haveta eventually die too don't they?

 

[KEITH KRAUSE]

There are superior carbs out there that fit your model. New and used.
You'd have to ask those that have made this change though.
Most often, the reason people change carbs is to increase performance. But to justify the change, you would normally go with pod filters, free flow exhaust, maybe racing cams and larger pistons, etc. You'd have to completely re-jet/re-tune.
Only you can inspect your carbs to see what condition the diaphragms and other parts are in. If the bike has sat a long time unused, this accelerates rubber hardening/cracking. If exposed to moisture, white fluffy corrosion can ruin surfaces. Most often, new o-rings and a good cleaning, followed by float level adjustment, carb synch, etc, will be all that's needed. The brass parts should be fine. But if you find the diaphragms are going or you have some metal corrosion, then that can change things economically. Finding a used set of carbs can be risky though too. They could be butchered by the PO.
I don't know if you need to make this change anyway. Get the carbs vacuum synched, along with the valves, etc, first. See how it runs. This is all basic maintenance stuff. Unless you really do see carb damage. So far from your descriptions, your carbs don't sound bad. Inspect them completely to make a good decision.

 

[LW_Icarus]

I am unbelievably, outrageously, happy right now. I stayed a lil late at the bike shop, talked the oldest mechanic there into helping me, he started in '81, and in 45 minutes it was purring like a kitten.

I started by hooking up the gauges to synch it, and I was probably just lucky but the bench settings were spot on. so we yanked the carbs apart and he ran a little wire through the pilot jets, I had looked to see if they were clear before, and they were but apparently not clear enough. put em back in and reset the idle mixture and its fantastic.

makes good power off idle to as fast as Ive spun it, didnt take a plug read or anything but Id say its damn close to being perfect. rode 50 miles today, smiling every second of it.

thanks for the info on the carbs, now that shes running Ill shelve that idea for awhile, Im not looking for any more power really, just reliability. a 4 into one may be in the future, but not till the stock exhaust gives up the ghost.

Damn Im happy my bike runs