1984 VF750 Interceptor problems. Dies from idle to 3k.

Hello fellow VF riders! So I have some problems. My '84 Interceptor 750 starts on choke and idles, but dies with throttle. The bike will not run off choke warmed up. When I can get the rpms to go above 3k it will rev up fine, it's 1200 to 3,000 that is a dead zone. This week I've had the carbs out twice for super cleaning and now I'm stumped. Could this be a CDI box problem? Coils? I've got new gas and new plugs in. Thanks in advance!!!

 

carbs sync'ed? check your insulater boots.. make sure they aren't cracked....

 

Did you disassemble the carbs when you had them out for super cleaning? Sounds like you have some clogged jets/passages. On an inline 4 I'd be looking at pilot jets, but the VFR is a bit different, but I'd be looking at full disassembly and thorough cleaning of jets and passages. Some of those things are really small.

Has it been down for an extended period? Or been running fine and now runs badly?

 

Carbs are not sync'ed, figured she should get the dead zone figured out first. Boots are good, no leaks. Did a thorough cleaning but didn't separate. The guy I got it from disintegrated some diaphragms, so that was the initial goal to fix. Got those in and did the cleaning, which allowed the reving, but still cuts out at the 1k-3k range. I'm in Minnesota where alot of people don't know how to store a motorcycle properly throughout the winter. I went through all passages I could, even the nasty tiny ones, and visually saw carb cleaner running through them through different origins...

 

Okay, you could have the passages cleared but unless you've pulled all the jets and cleaned each one you can depend on the fact that some of them are clogged. The holes in some of those jets are so small that cleaner won't really get to them to break the crud loose. You basically have to take them out and soak them in carb cleaner and clean each orifice separately. I guarantee you that after you've done it once, you make sure you never have to do it again. DAMHIKIJK. :soap:

 

My old jap inline twin does that when its low on fuel in the bowls. usually when Im low on gas and have to switch petcock from main to res.

 

Your pilot jets are clogged. You need a #12 steel guitar string to push thru the jets to verify that they are opened to the proper diameter.

carb porn:
http://vfrworld.com/forums/showthre...-Fuel-and-Air-Circuit-Identification-and-Porn

cleaning carbs:
http://vfrworld.com/forums/showthread.php/22449-Cleaning-carbs

 

Just to be clear, all removable jets have been cleaned...twice. They have soaked in carb cleaner each time.

 

One thing worth mentioning is that is has dual supertrapps on it and have no idea if it was re-jetted.

 

Just to be clear, soaking them in some autoshack-brand carb cleaner will not result in jets that are clean--they must be verified to be open to the correct diameter by inserting a metal rod of that same correct diameter.

It may look open to you but if it is not the correct diameter then it is still clogged. Your symptoms are classic clogged pilots--runs on the choke and above 3k but fails during the transition.

i've had guys bring me a rack of carbs that they swear were clean, hell one fellow said he 'cleaned' them 4 times.

How would you know if it were re-jetted if you didn't measure and write down or recordize your findings on a piece of paper, then compare to OEM?

 

Okay kennybobby, looks like i'll have to try the third time charmer on the pilots. I did not recordize on a piece of paper the size of the jets, so I don't know, I'll do that too. Anyone know what the jet size should be for SuperTrapps?

 

Carbs out, c'mon high E guitar string! Have to go to the local guitar repair store. Stand-by...

 

Consider this case closed! Thanks kennybobby for being on it! Carb #3 was a tight squeeze for the guitar string. A yellow dust puff ensued from blowing on it. I am a happy guy! Have a good weekend all and ride safe! - saltydog