Bought A 93 Vfr750, It Wont Start Anymore

So just got a 93 VFR750 last week, it was running great when i went to test ride it, and it rode great when i picked it up. Over the next couple days i was having some trouble getting it started in the mornings. The first time i just thought, ok this must be how it starts in the cold; but it got worse each time. First couple days i could get it going but it took a long time, but now i cant get it to start. I tried again today, with a fully charged battery, with no luck. About the only thig it did today was back fire a couple time. But when its warm it starts just fine. After reading here it seems like i might have a bad R/R. So unless there is other sugestions i am just going to order a new one and hope for the best. I was wondering where to get one and what type is the best?

 

So it spins over fine and won't start or? I'm not so sure you need an RR just yet. sounds more like it's in the choke system. we'll need more information to get closer to the culprit.

 

yea it basically spins but doesnt start. my first thought was the choke or carbs and such but i guess i got a little paranoid after reading all the stuff about the rr's

 

How long had the bike been sitting before you bought it? After the bike has been run and it's warm, does applying the choke have any affect? This will tell you if the choke is working or not. See what that does. If the bike wants to stall or it loads up the choke is OK. I would replace the spark plugs first. and then you may want check the fuel. Make sure it's fresh and drain the carbs while you have the tank off.

 

The R/R has nothing to do with starting problems if the battery is cranking the bike.

It sounds like your carbs are pretty gummed up, but once the bike is warmed up, the bike will run somewhat OK.

If you want to give it a try - SeaFoam is pretty popular for cleaning carbs without removing them. It won't do a super job, but it might fix your problem.

Like others have said already, once you get it running, play with the chok and see if it changes how the engine runs. That will give us a better idea as to what the real issue is.

BTW - these bikes are pretty cold-blooded, they need full choke from the beginning to start properly. Don't shut it off for at least 1 minute after starting the bike, and the RPM's have risen to 3,000 on their own.

 

I cannot remember if that year has a fuel filter may it may be a good idea to replace that and take the old one apart and look for rust or other crap. Also I would run a can of seafoam through the tank.

 

it's important that you don't twist the throtte at all while starting.....

test that your fuel pump is working

 

The bike turns over- Battery and charging system are OK.
The bike backfires- Spark coil is probably OK
The bike starts on warm days, but not on cold days- Probably a faulty enrichment/choke system

I believe that the '93 used constant velocity, carburetor types: Keihins (36mm).

First check that the choke cable is engaging the enrichment circuit. (You are using the choke in cold weather?). You will probably need to remove or prop up the fuel tank up to see if the enrichment thingy is moving in and out of the carburetor body. If these are not moving, then figure out why and fix. If they are moving freely, then you may have to remove the carburetors and inspect/clean them.

Good luck.

 

not sure how long it was sitting, owner said only a few weeks. the choke does have an affect when its running. spark plugs are good, just replaced those. the fuel is fresh, i went through a couple tanks when it was running.

i picked up some seafoam today but its not gona do much good if i cant get it running lol

ill check out the filter, is it pretty straight foward to change it? i couldnt find anything about it in the service manual. where can i get a new one?

how would i go about testing the pump?

 

pump? drain one carb through the float bowl screw leaving the screw loose, then crank motor. you should hear pump clicking and see fuel dripping from carb

 

How cold is it when it won't start? Any possibility that the fuel inlet valves (carb needles) are leaking?

 

probably just got the carburettors flooded when trying to start it cold and twisting the throttle too much.
sounds like you need to give it a day in the dry then choke on, ignition on, kill switch in off position, press start
wroooommmm

happened to me before

 

SirRodger may be on to something here. This may simply be operator error. Have you got the owners manual? Look up cold start procedure. You might be going about it all wrong. You did say it runs well when warm and you have already gone thru a few tanks of gas. That's easily 500mi. Is the gas mileage good? Like 40-45mpg? Runs on all 4 cylinders no popping or backfiring? We're all assuming the bike is stock, with no mods to jetting.

 

its about low-mid 40's in the morning.

i actually did this once by accident. a friend came over and he switched the kill switch to off, and i usually dont mess with it so when i went to go try to start again nothing happened lol. but ill try again when i get home today.

gas mailage was in the mid 40's. i rode it a lot the first couple days, and it seemed fine to me. previous owner installed a tbr pipe (the left side high mount if it makes any difference) and a stage 1 jet kit.

 

Like I've said before - my bike will NOT start without the choke. I KNOW my carbs are clean, and my gas is good. Don't touch the throttle until she has some temperature in those pistons. And DON'T attempt to start it without the choke!!!

The fuel filter on my 4G is on the left rear subframe. It's pretty easy to get to once the rear fairing is off.

If the bike was popping and backfiring when it WAS running, AND has a stock pipe, there's something else going on with the carbs. My bike snaps and barks on decel, but I have a slip-on with no jetting.

 

i always use the choke on startup. got used to that riding my ninja 250 through last winter in 20 degree temps.

 

so, yesterday i dumped some seafoam in the tank. and tonight I went to check out the fuel filter and pump, and put in a new battery. filter looked decent and pump seemed to be working fine. put everything back together, stuck the new battery in and vroom. now I still don't think it was just the battery cuz I had the other one charged up completely and even tried to jump it once with no luck. I'm gona get my mechanic to check it out still.


Thanks for all the help.

 

little update, i got the bike to the shop last week, called to check on it today. the plugs, that i had just put it, had oil on em. and he said the carbs were extremely clean. he said he should have it running tomorrow.

 

that oil might not have come from the combustion chambers but from weeping gaskets on the valve cover

 

Or it's not oil but fuel dissolved carbon from the combustion chamber from trying so hard to start it with weak or intermittent spark. If it happens again, I would have a spare plug handy. Pull off a couple spark plug caps and use the spare to check for spark.

You mentioned the kill switch which could be another "suspect". With infrequent use and colder temps it's possible the contact for it inside the handlebar housing isn't very good...or it's become oxidized. When you get your bike home in the garage play with the kill switch and see if it seems "oversensitive". If this happens again, activate your kill switch back and forth several times. I've actually seen this happen quite a bit. Your ignition needs GOOD battery voltage.

You may also want to check oil level or better yet, change oil, in case it got contaminated with fuel. If this is the case also check for a puddle in the airbox, and an oil fouled air filter.