OK, the bike, 92 F2, is bone stock. No mods. I’am trying to revive it after sitting for quite a while (years). I cleaned the carbs and it seemed to go back together without many issues. I set the pilot screws to 2 and a 1/2 turns out. All the Diaphragms looked good, a tip of one of the needle jets was really fouled but they cleaned up. The jets did not look bad, I soaked them over night and used compressed air on everything. Of course the float’s needle valves were all gunked up. One took effort to get out, but all cleaned up ok. The inside of the tank looks good.

New oil and new gas with some techron. I have not done the spark plugs yet.

It starts right up. It sounds pretty good.

However, when cold it will not go above 3k. It stumbles and hesitates badly when applying throttle.

I let it warm up and it will rev if I go kind of slow on the throttle. If I do a quick throttle it will stumble badly and can die pretty easily.

Any ideas on what I could have screwed up? Or something I haven’t done or replaced that needs it? Jets still not clean? Have been searching the forum, but no luck so far.

Thanks.

 

First thing I would do is change the plugs. Pull one and see what it looks like... Could be the sudden air fuel increase is too much for the foiled plugs to keep up with.

 

Thanks, Ya, I will. WalMart only had 3 plugs in stock when I picked up the oil LOL, so I kind of put it off. How are the plug wires on these, will they break easily? Anything else to look at?

 

I've never had a problem with them breaking. Never had an issue with coils either. When you pull the plug wire and plug make sure they arent soaked in oil. If so, its time for a new valve cover gasket. The oil will leak past sealss down into the plug wells and foul out plugs quick. But if you havent noticed any other oil leaks then you should be ok. Only other thing I can think of is check for any air leaks around the carb boots or airbox. those are a major pain when trying to figure out a carb issue. Once you get it to rev or stay running, you may have to adjust your pilot screws. The factory recommendation, if im not mistaking is just a base to start.
I'm sure someone else will chime in with their suggestions. The people here love to help. However it will cost ya, pics of the bike, its our fix lol

 

+ 1 on the plugs.

Also 303, if you are running an OEM-type paper air filter, dial your pilot screws to 2 3/4 out for a California bike, or 2 1/8 for all others (except for Canucks, which are 2 turns out! ), so at least your starting exactly where you should be.

On the plugs, you've got about a 5 thousandths of an inch to play with (.031 to .035) but I've always had the best of luck with them at .034 or .035 gap.

Good luck, and get some pics up of this thing, we likey pics.

 

Oh, and, welcome to the forum!

 

Hey, thanks for the inputs. I was delaying the plugs until I had a better idea of what is going on, but now with your feed back I'll just start on them. Great info on the gap.

Yes, the stock air filter. I think it is a Califonicated bike, so ya, great ...

It idles great, and I don't have to do anything to keep it going. It just will stumble bad on a quick throttle input. Slow throttle (after warming up) will rev.

I'll see what I can do on the pic front, just to get you guys going it is the black/purple model. I had a great (at least to me) sunset photo of back in the day. I'm not sure where I put it in the last move though. But, I'll get something Just not maybe right a way, she is neeked! LOL

 

 

Quick update. Did the spark plugs tonight, no difference. Still can not get over 3k rpms when cold, and after warmed up a real slow throttle will get me above 5k, and at that point it goes really well. Under 5k it stumbles and will die on a quick throttle.

I'm really leaning towards the jets. Anything else on that effects under 5k rpms?

By the way the plugs did not look bad, and I went with the same NGKs at .035

 

Diaphragm carbs are supposed to control the rate of the slides opening. Example: if you whack open the throttle, the diaphragm will only let the slide open as far as the engine vacuum will allow. If, for some reason your diaphragms are damaged or not seated, maybe the slides are opening too far and too fast.

It does sound as though your idle circuit is not working and perhaps you have an issue with the choke as well. There could be crud above the pilot jet, in the carb itself. As you get above 5k revs, you go onto the main jet circuit.