Hello all.

i have a 1998 vtr1000 with 22000 miles on it.

My bike will start up perfect every time. when it gets up to full running temperature ( 10 minutes in the driveway, or 5 - 8 minutes on the road ), the front cyclinder will completely shut down, and continue to run on the back cylinder. The first thing i did was change the spark plugs. after that didnt change anything, i used an in-line spark tester. When i have the failure with the tester in, it visually to the human eye it looked like i was getting good fire. next, checked the seal between the carbs and the manifold for leaks with propane. nothing happened. I then completed a compression check and got 120 PSI on both cyclinders. next, i had my coils tested at the honda shop. they were tested as good. i replaced the front coil anyways just in case. 57 bucks. so now, i thought maybe a had a bad CDI, so i went ahead and bought one out of a junk yard and it reacts the same way. i still have the failure when i get up to running temperature. After all this and some money, i am lost!!! has anyone else dealt with this problem or maybe have some knowledge to lead me further??!! thanks for the help!!


and if anyone wants to buy a CDI just let me know.

 

whew! I thought you meant someone had ripped it off.......

 

hahaha i wish... that would be easier to fix man! because all i can do is -->

 

Make sure that you carbs are synchronized.
Have you ever checked those valves clearances,they get tighter with time, the compression test would be meaningless since the engine was off for a bit.
If you had clearances checked, by a shop, the front is a real PITA to do, so they may have got a case of beer instead. If it's the case the compression should drop as the engine gets hot.
Other than that what the plug looked like colorwise ?

 

i have not checked the carb sync, nor am i not sure how. i have a book ill look at but any advice would help. and i dont know how to check the valve clearence either. so i asume its better to let a shop do? that has never been done. my bike hasnt seen a shop since ive had it except for tires. i bought it from a guy at the beginning of last summer who may have, but it also only had 8 thousand miles on it. i put about 14000 on it last summer and did all the general maint. myself.

 

I have a feeling this is fuel related, maybe even PVLIR. First, check the small vacuum line is going to the REAR nipple on the petcock, NOT on the bottom vent nipple. Next, do a "bench test" of the petcock by removing the fuel lines (or even just one) and installing a temporary line running to a cup or something. Then hook up another small line from the petcock vac line to a MityVac or similar. Ensure fuel flows freely from the fuel line. If not, then check that the petcock manual valve is fully open. It's an 8mm box end wrench that you need to operate it. I think it goes CCW. If all checks out there you need to keep checking components, including the carbs. Could be you have a stuck float or clogged line. Let us know how things work out for you..

 

thanks yall. i will try these things out as soon as i can and get back to you. all in good time.

 

+1 on the little line on the side of the petcock, NOT THE BOTTOM. It will do almost exactly what you are describing if the line is on wrong.

 

oh yeah + 1 on this, it could be fuel related too.
Check the easy stuff first

 

thank yall.. ill work on it when i get off work today and get back to yall tonight or tom. night

 

well, i just so happen to run into an older bike tech in my business park where i work. he used to work for suzuki and they flew him around to all the bike shops around the states to troubleshoot problems the local bike techs couldnt figure out. so, he now has my bike in his garage looking at it ( he now works on bikes on the side ), primarily to adjust the valves to see if that would fix it. We started it up till it had the failure, and he immediately said it was the carbs. im going to go ahead and let him work on it for me ( im not used to that ) but i am pretty confident he will be able to fix me up. Ill let you guys know what he does to fix it.

 

My bet: your front carb slide is sticking.

Have the tank/airbox ready for quick removal. Warm up bike and run around neighborhood till it runs bad. Pull airbox and see if one of the slides hasn't returned to full rest position. Possible causes: hole in rubber diaphragm, dirty slide/guide, weak spring.

 

Good call on the fuel Greg!

Speedhawk, it like she's running the front bowl dry and can't keep up starving the cylinder of fuel...your personal mechanic will fix it...man I wish I had my own personal mechanic!

 

hahaha i wish he WAS my personal mechanic... im still paying him. I just met him the other day and he seems to be pretty good at the trouble shooting and he rides a super nice bike so i know he wont scratch mine to hell. He has an 02 zx12 with nos and a wicked ( supposedly $3000 paint job ) air brush paint job. nice shop too.

 

well, remember i tested the rubber seal between the carb and the intake manifold with propane and nothing happened? well, it wasnt good enough. that dude had the tank off and had it running off of gas in coke bottles, sprayed the seals with carb cleaner and the bike bogged down big time. he orderd me some seals from honda and im going to put them on myself at home in the garage... repair bill was gunna kill me! i hope that is the only problem and fixes it..

sound like the problem to you guys?

it is the front cylinder seal so i bet thats it. and im sure that the aluminum manifold is expanding when it gets hot, breaking the carb seal, and losing power to the front.

 

Speed, that sounds like the culprit! We all figured it was a fuel prob

 

The front diapraphm is the first one to go in the carb.

It will run fine at idle but bog when on the gas.

The loss of vacuum will not allow the carb butterfly to work correctly.

Easy to see if you watch the butterflys when you open the throttle.

 

Hmmm, even my '98 with 45k miles has carb boots that look like almost new. I'm thinking that maybe the carbs weren't seated all the way or the clamp(s) were loose. But that's just me thinking "out loud".

 

yeah i dont see any "visual" problems with the boot and i dont get my parts in till thursday

 

Are the small foam air filters still in place and clean in your air box?

 

i am not currently home.. when i get back this afternoon ill make sure and let you know8541. at this stage i am open to ANY suggestions. has anyone else had any fairly serious break downs like this by 22,000ish miles? not that this may be super serious, but it sure has been keeping me from riding for a long time!

 

im still waiting on my new boots but:

Question: on the inside of the boot ( front AND back ) you have the little metal ring housed in the middle. there is an indention on one part of the metal ring that looks like a little flat spot. the flast spot IS on both the front and rear cylinder boot.

haha i can only study the bike and parts and clean on the bike so much while im waiting of freakin parts to come in.

 

I changed the carb boots on my 2001 VTR a couple of weeks ago. I had the carbs off and I had new carb boots which I had bought "just in case". There was really no need to change them. The originals looked fine and I didn't have any carb sealing issues.
I noticed that the originals had the metal rings with the indentations Speedhawk mentioned. The replacements didn't. There's another unsolved mystery.
A couple of years ago when I when I put in a jet kit I did have a problem with the boots not being seated properly. It was my oversight and there was nothing wrong with the boots. Anyway, when I used some volatile spray in an effort to see if the leak was fixed, I don't know if was brake cleaner or starting fluid or some other poison, the motor would bog. It may not have been the leak that caused the bogging. Air flows into the air box after being sucked up beside the carbs. The vapour being sprayed would be sucked in too. I removed the snorkel from the air box and installed it so the open end pointed up rather than down. Sprayed again and no bogging.

 

something else i noticed last night that MIGHT be related to what comedo is saying. the guy that looked at my bike sprayed carb fluid on the boots. it bogged down. but what i noticed last night is inside the air box under where the filter sits, there are those two foam "filters". im not sure what they are, but one is busted. any relevance? maybe its sucking in something it shouldnt ( like carb cleaner mist ), or maybe i have some of that foam in my jetting?? it wouldnt make it bog down only when the bike gets warmed up, but you never know.

any feedback?

 

The rings should be in there... they are basicly there to stabilise the boot to avoid leeks... swap them over from your old ones if you dont have them on the new...

Unlikely that you have foam where it doesn't belong... but again, it's supposed to be there and not having it will make the bike run badly...

 

here is the foam peice in the air box i am talking about.

 

I believe those foam things filter the incoming air into the carburetor "air vent tubes" I'm not 100% sure what the air vent tubes do but I think they go to the top side of the diaphragm.

Part number is: 17254-MBB-000
Description FILTER, SUB A/CLNR
Price $1.55

Information is from RonAyers

 

thanks again. should get my parts in today and put the old bird back together enough to see if it runs!

 

the guy never got my parts in friday!! BUT EVERYONE: just FYI on my problem. I pulled the valve covers this morning to check my valve clearances and i am okay on the rear cyclinder ( which has been running fine ) on ALL clearances.. and the front ( the problem child ) was great except bikes right side exhaust valve. the book calls for 0.28 mm to 0.34 mm and i was reading a slightly tight 0.35. does anyone think i am alright on this or do i need to shim it??

 

No it's perfectly fine, good thing you had them checked, a too wide clearance makes a pretty audible ticking sound.