Hi!! I have a Honda trx70 that has a carb problem. Ignition is firing fine and the quad starts on the first pull all the time. Idles like a champ. It does have an occasional miss at idle and if I try to punch the throttle hard the motor just bogs like it isnt getting fuel. Then I release the throttle and it idles perfect (except for the occassional mis). If I spray ether in short blasts every few seconds into the air box the mis goes away and I could punch the throttle and it revs up nice. So its a fuel problem. I'm not new to rebuilding carbs and this one has been done perfectly. All parts replaced including the float and all passages are clear. I even tried to move the needle clip position to the forth notch to improve the midrange but that didnt help. Could there be something wrong with the carb casting?? Any ideas?? I dont think its a compression problem because it starts on the first pull. I did a compression test with one of those push in testers and it reads 125 plus but I cant get a real tight seal so it would be alot more. Any help would be greatly appreciated.

 

Well first off it sounds like your running lean. You moved the clip holding the needle in which direction? How does the plug look? Most motors will hesitate if you try to punch them from an idle. It takes a second for the motor to respond to the opening letting air and fuel into it. You can try to "aim" the opening on the spark plug gap towards your intake valves which might help in the slightest bit.

 

Yes, I definitely think its a lean pop. I move the needle clip down to allow more fuel in on the mid range. The plug is a whitesh tan color even after my daughter drives it around for a half hour. She is using it with the throttle stop limiter and only first gear. She's new at it. When I put it away then I take off the limiter so I can rev it up and try to figure it out.

 

You're definitely lean. Try going up a main jet size and see if this helps any. If it does, keep going up main jet sizes until it skips on the top, then go down one. Have you done any modifications to this quad? Is the jetting stock? If you have done no mods and you are running stock jetting, I don't see why you should be having problems. Check to see if the air filter is on properly. If it's not, that could be creating a lean condition.

 

Yes, the bike is all stock with stock jetting. Everything is redone in the carb including the jets. I was wondering if there could be some sort of internal problem with the carb even though it looks great. I'm considering buying a brand new carb but was wondering about doing the jet trick. Should I up the size of the main and idle jets? Because there is a problem at idle (miss) and high speed (bog). THanks

 

I currently dont have an air cleaner connected. Just to make sure that wasnt the problem.

 

It sounds like you're lean on the bottom end, and rich on the top end. Make sure your air filter is connected and well oiled before doing anything because it will be lean if the filter is not on. Try to fix the bottom end first. If the carb has an air screw, try turning that in a half turn at a time with the wngine running and warmed up. If it has a fuel screw instead of an air screw, try turning it out a half turn at a time. If it gets worse, go the other way. If these external adjustments don't help, try changing the pilot jet. Go up one size with the pilot jet and see if it helps.
If it's bogging on the top end, it's probably rich. Go down one main jet size and see if it helps. You should not have to change things too much if everything is stock. Go down main jet sizes until it stops bogging on the top end. After making these adjustments, take a look at the spark plug. If it's light or white, then it's lean. If it's black, it's rich. Good luck.

 

make sure the valve lash is set right.if nobody adjusted the valves ever the intake has no gap and needs to be loosened,,,,then it will run perfect.also check the pilot jet is not clogged. ill bet its the intake valve is to tight if ya dont know how to do it email me at jimishadow@yahoo.com