Sputters and stalls at top end....definitely Carburator

[The_SHOW]

OK, I've read everything and have tried everything and now I'm finally posting.

I have two Sprees ('86 and '87), both with under 800 original miles but have been sitting a LONG time. I got the '86 working just fine but the '87 sputters and stalls at top end right at 25 mph. After the stall there is difficulty starting again and I have noticed fuel flooding out of the carb sometimes.

After cleaning the carb with carb cleaner AND compressed air, (The 2nd time with compressed air. A total of 3 cleans really.), I decided to swap fuel valves with my '86. The '86 still works, the '87 doesn't. Swapped fuel lines and the'86 works, the '87 doesn't. Swapped carburators and the '86 does not work, now the '87 works. At which the carb was cleaned for the 3rd time; all jets cleaned and clear, float checked and no fuel overflowing out of carb yet. However, the '86 now sputters and stalls at exactly 25mph. Same problems are now on the '86. I am lucky to have two sprees, one working, so I can do this trial and error. I would like to save money by not buying another carb cuz this must be fixable but how???? Any help would be greatly appreciated! All parts are original and they were both working perfect before storage.

Also, are the '86 sprees softer and smoother sounding than the '87? I feel the '87 has more pickup but is definitely louder and not so smooth.

[MySpree]

if eventually you need a carb, ask me. all my carbs have been cleaned and tested.

[noiseguy]

Sounds like you've root-caused down to the carb.

Check the main jet size (should be #65) and needle jet position (unless you didn't swap that.) Also, check your fuel float level. I believe this procedure is in the manual. You are either running out of fuel or air at the topend. I'm guessing your main jet is dirty.

It sounds like your '86 muffler is dirty. Plugged mufflers sound "smoother." Read tech docs for how to clean. Also check your exhaust port and head on the '86 for carbon; if the muffler's carboned up chances are the rest is too (odd at 800 miles; bad oil maybe?)

[ferchja]

My $0.02 if you didn't swap the bystarters then its a jetting issue (clogged main jet, wrong size), if you left the bystarters on the carbs, then its a vacuum leak on the oring at the bottom of the bystarter. If you replace that oring ($0.25 at the local hardware store) and it still is an issue then go to the main jet cleaning/change size. The needle on the throttle is mostly for fuel mixture between idle and near full throttle, so if that is set to the correct starting position then you should be ok, and since the problem followed the carbs and not the throttle cable (position) then I would assume it is fine.

At full throttle its air and the main jet, nothing else, so if air is getting in behind the throttle (i.e. the bystarter) it will cause the top end to run rich, which fouls the plug causing it to start to cough

I doubt it is muffler related since you did swap it to a different bike and the problem followed.

[The_SHOW]

So, thanks to the great advice I received from Noiseguy and Ferch, I swapped the main jet (both #65) between my two Sprees. Sure enough, this affected which Spree worked. The one that worked before doesn't after the switch and vice versa. The sputtering at 25 mph continues on the one that's not quite working right.

Now what? I examined both jets on removal and found little difference between the two. Both holes were open and clear, however, the one that isn't working properly appeared to have a different color. It looked almost oxidized or wax-like. I sprayed carb cleaner on both of them before reinstalling them and the problem seems to follow that jet. What could be the problem in performance here? I'm going to try it one more time to be absolutely conclusive but I can't understand why this one jet isn't working.

The carbonized muffler and head sure seem to make sense about the sound of my '86. Thank you Noiseguy. The cleaning of the muffler sure seems like a production. We'll see if I get to it or not. For now I'm concentrating on this jet and trying to understand how it works. Can it be saved or made sense of? At least I won't have to buy a whole new carb, but lets see if anybody can figure anything else out.

Thanks for everybody's help!

[ferchja]

Can you read the numbers on the side or bottom of the jets? Are you sure they are 65's. If the jet has any burrs inside from trying to clean it that will effect it. Also the older a jet gets, dirt particles will start to widen the hole just slightly enough to cause it to go rich.

Order a #65 ($5 at the local honda dealer) jet and you will be smokin'. It sounds like the one with the problem has become oversized causing it to run rich.