I just purchased a 93 900rr. When i picked the bike up from a shop, they had been through the carbs and done a thourough cleaning. The bike starts and idles just fine and runs great until you reach 6000 rpm under a load. The bike then just breaks up and will not accelerate past that. They then changed the plugs and it did nothing to help. Would and of you care to give your opinion on what you think it may be? I am thinking it may be a coil issue since the carbs and plugs are fine; the air filter looks to be fine. You have gas, air and spark, those are the only options i believe. I was going to try to tackle this myself since they did not catch this at the shop. I have a factory repair manual on the way, i am very good at troubleshooting issues and i have electrical system experience; i believe i could figure this one out since i have the tools i need. Any help from you guys would be great; i will post a pic later; got a great deal on the bike 3000 with only 7700 miles never been down, dynojet kit with a pipe made by dynojet that works very well, some other small add ons.

James

 

bump bump bump

 

I had a GS750 that did that. It turned out to be the coil.

 

It can be air, fuel, or spark. you can try replacing the coils as suggested. Check the airbox for air obstructions, make sure the air filter is clean. Fuel filter clean? Carbs jetted improperly possible. The main jets should be #122 or less.

 

Also make sure the airbox is 100% airtight. A leaking airbox will cause poor performance. I sealed mine with rtv silicone.

 

turned out to be the coils, bike runs f-in great now

 

I'm not going to ask what's the top speed you had done since it's a taboo here...

 

Go to a different shop next time, is my advice.

A certified Honda tech would not miss something like that.