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1998 VTR runs rough at high rpm under a load

Old 05-08-2013, 06:43 PM
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1998 VTR runs rough at high rpm under a load

I recently purchased the bike (I work at a Honda motorcycle dealer so itís not my 1st bike but it is one of the oldest Honda and my 1st vtwin sport bike) I cleaned and synced the carbs, checked the coils, put new plugs in it and a new reg/rec but it still acts like its dropping a cylinder above 5 or 6,000 rpms under a load. When itís on the stand it revs up and runs fine. Iím scratching my head so any tips would be helpful. Thank you
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Old 05-08-2013, 06:45 PM
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Sounds like it might be the petcock diaphragm.
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Old 05-08-2013, 06:54 PM
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Originally Posted by 8541Hawk View Post
Sounds like it might be the petcock diaphragm.

I also thought that but i put a fuel bladder around my neck and went down the road and it still did it. I have a feeling its electrical???
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Old 05-08-2013, 06:57 PM
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Then check the pick up sensor in the clutch cover.
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Old 05-10-2013, 12:57 PM
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Originally Posted by 8541Hawk View Post
Then check the pick up sensor in the clutch cover.
would that effect the ignition? I was thinking side stand switch posably. I rode it in to work today so ill do some checks and see what i can find.
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Old 05-10-2013, 01:07 PM
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Originally Posted by masonftp View Post
would that effect the ignition? I was thinking side stand switch posably. I rode it in to work today so ill do some checks and see what i can find.
It's the pick up for the ignition rotor, so yes it can effect the ignition.

The side stand can cause similar issues but the fact it only happens at high RPM & load would point to more of an ignition issue as you have ruled out a fuel issue.
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Old 05-13-2013, 02:19 PM
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Originally Posted by 8541Hawk View Post
It's the pick up for the ignition rotor, so yes it can effect the ignition.

The side stand can cause similar issues but the fact it only happens at high RPM & load would point to more of an ignition issue as you have ruled out a fuel issue.

The clutch switch is working fine, put a new battery in it and the charging system is working 100%. One of my techs thinks it could be the ''unit converter'' that controls the coils. Im not about to throw down on new one not knowing 100% that its the real problem. I guess my next move will be to take one off a bike that works and try it. Not going to lie im really starting to hate this bike!!!
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Old 05-13-2013, 02:25 PM
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Does it completely cut out, of just bog down?

Some people have had the side stand bounce enough at certain rpms/speeds that the switch cuts out (effectively turns the motor of for a split second). If this is the case the test is to bypass the side stand switch... basically connecting the three terminals at the switch and riding it.

It's a small chance, but it could be a possibility. Don't hate on our bikes! We're quite fond of them!
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Old 05-13-2013, 02:27 PM
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I've heard of coils reading the right resistance but still acting up under load...
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Old 05-13-2013, 02:38 PM
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Well yours would be the first converter that I have heard of going bad..... and I've been around these bikes since '97.

So if you can locate one to try, give it a shot but I really doubt its an issue.
I do have a stock ECU you could try if you want to eliminate that also but I still think it sounds like the pick up. Name:  idunno.gif
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Old 05-13-2013, 08:27 PM
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Originally Posted by masonftp View Post
I also thought that but i put a fuel bladder around my neck and went down the road and it still did it. I have a feeling its electrical???
how did you connect the fuel bladder?
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Old 05-16-2013, 03:47 PM
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Originally Posted by zanoj883 View Post
how did you connect the fuel bladder?

Directly to the fuel line with a T connector.
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Old 05-16-2013, 03:56 PM
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Originally Posted by 8541Hawk View Post
Well yours would be the first converter that I have heard of going bad..... and I've been around these bikes since '97.

So if you can locate one to try, give it a shot but I really doubt its an issue.
I do have a stock ECU you could try if you want to eliminate that also but I still think it sounds like the pick up. Attachment 15491

Thank you I greatly appreciate the offer!! One of my co workers (works at our other store or i would have done it sooner) is going to let me barrow his and ill give it a try. I'm with you on never seeing one go bad and i have owned over 15 honda sport bikes.
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Old 05-16-2013, 04:02 PM
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Originally Posted by 7moore7 View Post
Does it completely cut out, of just bog down?

Some people have had the side stand bounce enough at certain rpms/speeds that the switch cuts out (effectively turns the motor of for a split second). If this is the case the test is to bypass the side stand switch... basically connecting the three terminals at the switch and riding it.

It's a small chance, but it could be a possibility. Don't hate on our bikes! We're quite fond of them!
It bogs down but it does it like a light switch consistently not like a carb issue that you can normally play with the throttle and keep climbing rpms. I checked the side stand switch and its good. I like riding the bike and I think the handling is amazing but Iíve never had a bike that I couldnít fix and that sucks
lol
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Old 05-28-2013, 04:39 PM
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barrowed parts from my friends bike but its a 02 or 03 so the electrical is diff. back to the drawing board
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Old 05-28-2013, 06:06 PM
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My chain and front sprocket are worn out and it acts like you describe, in my case it's the front sprocket slipping on the chain. Only under load, like 2/3+ throttle at higher rpms. If it hadn't happened to me before I would suspect carb or electrical problems too....

and yes I'm changing them tomorrow :-)
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Old 05-28-2013, 11:31 PM
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Originally Posted by masonftp View Post
barrowed parts from my friends bike but its a 02 or 03 so the electrical is diff. back to the drawing board

If it makes you feel any better, i'm having exactly the same issue!
Has improved slightly with new plugs, but am yet to solve it..
I'm going to try new coils next. Might do the stick coil mod on here, and see if that improves things.
Good luck, please post up if you manage to sort it!
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Old 05-31-2013, 03:55 PM
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Originally Posted by octanejunkie View Post
If it makes you feel any better, i'm having exactly the same issue!
Has improved slightly with new plugs, but am yet to solve it..
I'm going to try new coils next. Might do the stick coil mod on here, and see if that improves things.
Good luck, please post up if you manage to sort it!
I will and you do the same! i put a set of known good coils of another bike and i didnt help... such a weird problem
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Old 05-31-2013, 03:56 PM
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Originally Posted by VtrInMtl View Post
My chain and front sprocket are worn out and it acts like you describe, in my case it's the front sprocket slipping on the chain. Only under load, like 2/3+ throttle at higher rpms. If it hadn't happened to me before I would suspect carb or electrical problems too....

and yes I'm changing them tomorrow :-)

I wish it was that easy my friend but its def not a chain and sprocket thing
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Old 05-31-2013, 04:45 PM
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It bogs down but it does it like a light switch consistently
Have you checked the timing is all correct. It seems you have checked just about everything. It almost sounds like the timing is out by 180 degrees. If you described the symptoms as if it's got a limiter on at 7000rpm and the bike wont go past that then that would be it.

Pulling the cam covers off will show the timing marks lining up properly. It's how much the crank turns between firing pulses. If 180 out, the rear cylinder fires, then the front one fires 90 degrees later. You need it to be 270 degrees later. The fix would be to set the rear cylinder to TDC on compression, remove the cams and turn the crank 1 full turn anticlockwise until it comes back around onto RT. Then refit the cams.

As you have pretty much checked everything else I think the timing and valve clearances is the next thing to check.

I would like to know the end result to this issue. it's got my brain ticking over.

(:-})

Last edited by cybercarl; 05-31-2013 at 04:57 PM.
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Old 06-01-2013, 05:34 AM
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Since you don't know which cylinder is affected put it back on the stand, put it in 1st engage clutch and apply brake to simulate road going load. Pull the front plug wire first cuz it's easier to get at and if it bogs at 6k then that's the troubled one. If that one doesn't bog then pull the rear plug wire and test again. Maybe this would shed some light on the source.
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Old 06-03-2013, 02:57 PM
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Originally Posted by cybercarl View Post
Have you checked the timing is all correct. It seems you have checked just about everything. It almost sounds like the timing is out by 180 degrees. If you described the symptoms as if it's got a limiter on at 7000rpm and the bike wont go past that then that would be it.

Pulling the cam covers off will show the timing marks lining up properly. It's how much the crank turns between firing pulses. If 180 out, the rear cylinder fires, then the front one fires 90 degrees later. You need it to be 270 degrees later. The fix would be to set the rear cylinder to TDC on compression, remove the cams and turn the crank 1 full turn anticlockwise until it comes back around onto RT. Then refit the cams.

As you have pretty much checked everything else I think the timing and valve clearances is the next thing to check.

I would like to know the end result to this issue. it's got my brain ticking over.

(:-})

ill keep ya posted and thank you for the help.
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Old 10-05-2015, 03:36 AM
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Can I get a status on youre problem?

Originally Posted by masonftp View Post
ill keep ya posted and thank you for the help.
Hi. I just saw youre (old) post, and I have the exact same problem with my vtr. Did you solve the problem? Many thanks in advance.
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Old 10-05-2015, 08:45 PM
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I had a mechanic improperly install a cam after a valve adjustment and had a problem exactly as you describe until he fixed it for me.

Good luck
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Old 10-06-2015, 03:21 AM
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Oh, thanks for the heads up.

Originally Posted by SloBlue View Post
I had a mechanic improperly install a cam after a valve adjustment and had a problem exactly as you describe until he fixed it for me.

Good luck
I can write a little more, just in case it changes anything.

It runs rough from about 7000rpm more or less. And that happens EVERY time under load. I can climb all the way up to the top rpm on maybe 1/4 throttle. It always cleans up a little between 9500 and 10500. I am not sure if that is 100 percent or not. I bought this bike like this, so i have never experienced it working properly. I will list what I can come up with of things i did to it lately even though not everything has anything to do with the problem:-). I have changed the air, and oil filter, engine oil, cooling fluid, sparkplugs, checkt the coil and caps, cleaned the carbs, adjusted the mix screw to 2,5 turn open to se any changes (I'we heard this has only to do with low rpm issue, but testet anyways). I have also checked the vacuum hoses. The plugs looks ok too after a couple of months of use. The top speed is about 200km/h(125mph) @ maybe 7000rpm where it cant climb further. Thats about it

Last edited by V-Twin Torque; 10-06-2015 at 03:26 AM.
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Old 10-06-2015, 03:30 AM
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Do you have more info about the cam problem?

Originally Posted by SloBlue View Post
I had a mechanic improperly install a cam after a valve adjustment and had a problem exactly as you describe until he fixed it for me.

Good luck
Hi. And thanks for the info. Do you have more details about the gam problem? Did you have to adjust the valves also or just the cam?

Thanks in advance
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Old 10-06-2015, 01:51 PM
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This thread sucks. We read the whole thing only so find the OP never reported back.
banish it!!

When I bough this latest VTR, I had similar heavy throttle missing, popping on deceleration, rough idle, carb farts and stalling at lights. I took the simple route and had success. This included a stock filter element, removing oversized orifices and setting up per "hawk".

Last edited by Hangfly; 10-06-2015 at 03:37 PM.
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Old 10-12-2015, 06:28 PM
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V Twin have you checked the pet **** diaphragm on the vac side? When I ask have you checked it it'd am asking if you did a light check on it?
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Old 10-12-2015, 06:57 PM
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Not light checked:-(

Originally Posted by Meier Link View Post
V Twin have you checked the pet **** diaphragm on the vac side? When I ask have you checked it it'd am asking if you did a light check on it?
Hi. If you mean the diaphragm under the tank, I did, but not with light, no. Only visually should i check it again with light? I checked it extensively

Last edited by V-Twin Torque; 10-12-2015 at 07:05 PM.
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Old 10-13-2015, 04:28 AM
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Yes the diaphram that is in cased under the tank. The petcock assembly has three hoses hooked up to it 2 fuel lines and a vac line.

There will be 2 diaphragms a spring and a rubber cap in the assembly. If either diaphram is damaged it will cause a lot of head aches. I know this from experience. I did a visual check on mine and it seemed fine and my problems got progressively worse. Next time I pulled it apart I had a huge hole in it. It formed in less then a few weeks.

Also make sure you hook the vac line into the correct port when reconnecting. It goes to the rear of the assembly not on the nipple facing downwards.

Last edited by Meier Link; 10-13-2015 at 04:33 AM.
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