I have a 93 F2 and when I'm rolling on the power the bike starts to stumble around 4500 rpm on up to about 5500 rpm. Also, when I let off the throttle and the rpms are up, i get a little bit of a back fire. I bought the bike used and other than the mention problems it runs great. It does have a Yoshi exhaust system on it. Does it sound like the carbs need rejetting, or could it be something else?

 

Everything I've read and from what I've been told about my bike, you need the carbs cleaned, then checked to make sure they have the correct jets.

 

I agree with Mike's comments. Sounds like the jetting isn't correct to cover-up the stumble around 5k RPM. I have a '92 F2 with a Two Bros pipe. Stage 1 jet kit really helped in the midrange. I have too been noticing some backfiring when coming off the throttle. I believe that is a characteristic of it being too lean.?? I have also noticed my bike getting much louder over the years. I think it is time to get the pipe repacked.

First thing is to take the carbs apart and look at the needle jets and main jets. If you need it, I can look through my notes for my stage 1 kit which will tell the main jet sizes.

Good luck.

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Thanks for the info.

LitlleCBR, that would be great. I can check what your stage 1 kit had against what my jets are.

The stumble seams to happen after I have been riding for around 50 miles or so. I recently changed the air filter to a K&N, simple because I can clean it versus buying a new one, and havent had the time to go for a long enough ride to see if it helped with the stumble or not, but I did notice a little bit less of a backfire when coming offf the throttle.

 

back firing would be a to rich mixture usually. the un burnt gasses in the exhaust will ignite..

 

Here is a link to the Dynojet kits. Scroll down to the F2 model and you can view a .PDF on the kit. I will check which mains I have in mine.

http://www.dynojet.com/jetkits/hondajets.shtml

 

I agree with the backfire, but I think what he may be having is a popping sound at decelleration. IIRC, that indicates a lean condition.

 

I have 124 mains in mine. Needle position is in #1. The kit came 118, 122 and 126 mains with it. A guy at a localshop did a lot of work with F2's (with a pipe) and suggested a setup using 124 mains. We used that and put it on the dyno and looked good. I have been happy with it.