I have a problem with my 87 cbr. I first noticed this problem about 2 weeks ago after i replaced a few parts (ngk plugs, fuel filter, oil, and filter) now when i start the bike it runs fine, but once it gets to running temp after me driving for a bit it starts running weird. When i stop it will either die or it will idle very high, above 2 grand usually then slowely go down and eventually die. It seems a bit doggy also.
Im not sure what this could be, but im going to take my carbs off and clean them up and see if that fixes the issue. Im also running 91-93 octane and i read somwhere that i should be running 89, is this true? and could this be causing the issues?

 

1. Check fuel tank vent tube (clogged?)
2. Check carb syncronization
3. Check carb float levels
4. Clean carbs
Regular gas (87 AKI) is fine for this bike. Higher octane gas will NOT cause any running problems, it's just a waste of $$$.

 

how do i go about checking the float levels and the carb syncronization?

 

Let's not get crazy right off the bat. Eliminate the easy stuff before you start tearing the bike apart.

Here's the big question we need an answer to before any advice can be given:

Did the bike work PERFECT before you replaced all that stuff?

 

FALSE. Higher octane gas has the potential to cause HP loss under certain situations. It's not substantial on carbureted bikes, but can be noticable on injected ones. On top of that, you have to look at how your octane is being boosted. Most gas stations just add ethenol to their gas, which causes the tested octane rating to be higher, but doesn't actually offer any performance increase in real life. Look for the sticker on the pump that says "May contain up to 10% ethenol." If it's there, then you're paying for watered down gas. Gas stations that carry "real" high-octane fuel have it on it's own separate pump, just like they do with deisel.

You gotta remember, you're running on a 4-stroke lawn mower engine. 4 cylinders does not make it an Evo.

Hell, even the Evo manual reccomends 89 octane. Cars haven't needed more than that since the muscle cars of the 70's, and your engine is not producing anywhere near that kind of HP or torque. That's why they can get away with the watered-down lie now: no one will ntoice.

 

Wow someone is really mad about ethenol and octane stuff.

Anyways cleaning the carbs is a good idea. I would do that first.

 

took the carbs off today, i cleaned everything up. now i thnk i know whats going on, there are these black cylinders that move up and down with vaccum, the one on the far right doesnt move, i suspect that the rubber diaphram is ripped but i cant get to it because the screws on the cover are stuck in there good. anyone have input?

 

Man, I've been there.

http://www.walgreens.com/store/produ...sku=sku4252739

Those little things have gotten out screws that my Craftsman and Snap-On sets couldn't handle. I swear by them.

 

I think that octane is octane. There is a lot of confusion about octane numbers in America. The owner's manual for my bike ('91 CBR600F2) specifies use of 91 RON (Research Octane Number). The gas pumps in America specify an average of 2 octane numbers (RON + MON / 2) = AKI (Anti Knock Index). I recently called Honda tech support in California. They told me that 91 RON is equivalent to 87 AKI (i.e regular gas). My $.02.

 

These are standard service procedures detailed in the factory manual (available from Helm, Inc). You need a special tool (multichannel manometer) to do the carb sync, available from Motion Pro, Inc.