1985 vf700f with no power

it will rev up fine but when you ride it it struggles to get over 5000rpm, it does not have mufflers on it but i ordered them thought it might be the problem but i was just curious if there were any common problems

 

I doubt the mufflers (or lack there of) are your problem. It sounds like carb issues. What else can tell us about this bike? It's history? Has it sat for a while? Is it ridden regularly? When did this problem start?

 

i just bought the bike it has 25000 miles on it and i dont know alot about it. it idles very good and revs up fine. and when i bought it someone already cut off the mufflers.

 

Along with checking out the carbs/jets. Make sure the carb boots are secure. I've had them come loose and begin to suck air straight into the head making the engine starve itself at higher RPMs.

 

a missing air filter can do this too.......

try running a fuel system cleaner like Sea Foam through the carbs, and, if that doesn't help, you'll need to pull carbs to service.

 

I had the same problem. My issue was that the main jets were drilled out - way too rich - couldn't sustain combustion over 5K rpm.

 

is there any way to check that besides taking the carbs apart? like hooking up a vacum guage or somthing?

 

To check for a carb boot leak, spray wd-40 around the carb boots - 1 at a time. If the idle changes, you have a boot leak.

The only way to tell if the jets are drilled out is to compare them to stock jets. These jets are so sensitive that changes may not be visible to the naked eye.

Now if the PO put different jets in, the jets will have a number on the top. Compare it to the stock jet number.

Mine were drilled out to almost twice the size of stock - so it was easy to tell.

 

you need to check that bike is running on all 4 cylinders....check by (carefully) feeling each exhaust header. if one cylinder isn't working, there's your problem.......

 

Another - less injury prone method - is to pull the plug wire when the bike is running and see if the idle changes. If it doesn't change, you've found the culprit cylinder.

 

pulling plug on running engine can damage CDI box or coil, i believe, so plug wire should be grounded if disconnected.......

 

yeah i put the mufflers on and i still have the same problem i just wanted to rule that out so i will have to try to check everything out saturday when its daylight out still when i get out of work. also the guy i bought it off of said he just had the valves adjusted wondering if they adjust them too tight to the point where there not closing all the way maybe.

 

Pull the airbox top and start the bike. See if the slides are moving at the same time.

If you don't want to run the bike, just gently lift up the slide and let it drop. It should not SNAP down. If it does, something is wrong with the diaphragm.

A cut or incorrectly installed diaphragm will cause a slide to not move with the others - and cause loss of power.

Note, with the top off, the bike will not run well - but it will run.

 

ok, .....now you need to do a compression test on all 4 cylinders according to directions in factory shop manual.

as a matter of fact, a prospective buyer should make a compression test before buying any 'cycle....especially if it runs poorly or not at all or has high mileage.

having a sticky or non-functioning carb slide sounds like a good guess.

 

Squirrelman, not sure if you're being sarcastic or not. I'm just trying to help the guy out...

I don't have the factory manual.

Considering the condition of the bike I got when I traded in my Magna - I'm surprised the damn thing ran.

Almost everything was wrong with it and I've had to sort through it one by one...

the highlights:

bad gas cap
main jets drilled out
blown rear headgasket - then front headgasket
air leak in coolant system
fans not getting power

Now an oil leak from behind the neutral switch I have to get a seal for.

Based on this bike and the 8 years maintaining the Magna I had, i've experienced a lot of what can go wrong on a bike.

 

ok so i pulled the carbs off when i got home from work and i found that 2 of the vacum tubes or diapraghms are ripped and the other 2 dont look very good there all swelled up and mushy so i am going to assume that this is my problem considering that they control the seats for the jets. but does anyone know where i can get them besides the dealer because my buddy bought some for his shadow and they were 100 a piece. thanks

 

Yeah, that's bad news. Figure on $80 per peice for those diaphragms. On the bright side at least you've figured out the problem!

 

that's nutin..... i know a guy who broke a diaphram, and he's still paying 18 years later!!

 

Cold hard truth (until I see a pic): you bought a POS. Why would you buy something without mufflers? Sorry, I'm not trying to be an ass. Hope you didn't pay too much.

 

no i didt pay anything for it i traded a 97 cr250 for it and i only had about 600 into that cuz i bought it for 100 and the interceptor is very clean