1998 VTR runs rough at high rpm under a load
10-13-2015, 05:03 AM
#31
Junior Member
Squid
Join Date: Oct 2015
Posts: 8
2 diaphragms?
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.
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.
10-17-2015, 04:03 PM
#32
Junior Member
Squid
Join Date: Oct 2015
Posts: 8
Checked...
I will check the whole assambly again. The vac line is on the correct nipple. If I cant find anything, my next step is to check cam position and adjust the valves while in there... Thanks for the help so far. I am really getting tired of this problem:-( i have been driven like this for four months now. The owner before me, had it like this for two years:-/ I hope I will figure this out soon:-)
This weekend i adjusted the valve clearence to optimum position, and checked cam positions. It runs a bit better and smoother, but still the same problem:-(I have now ridden the bike a lot on high rpms today, and it got a lot worse. It runs on one sylinder most of the time, but runs on two when over about 2/3 throttle. I remember i had this same problem with an outbord engine i had once. Ended up being a bad coil. Fuel, sparkplugs and caps, air and all that is fine. I am now 95% sure it is a bad coil. I have tested the ohms on both coils some weeks ago. Was bad connection but fixed it. By checking the resistance, I can check connectiveties, but thats not good enough. I will get some new coils, and get back to you guys. Thanks for the help so far. Sorry for my English btw
12-30-2015, 07:46 PM
#33
Junior Member
Squid
Join Date: Oct 2015
Posts: 8
Still the same problem:-(
Hi again.
The problem is still here:-( the reason it only ran on one sylinder was from cooling fluid spraying over the plug caps(I think) i filled it too much up before testing. After a while it dried off and worked as before. Still struggling with under high load and high rpm. Back to the drawing bord.
I have not synced the carbs yet
and will try new cdi box if it not works after the carb sync. That is about the last things that can possible couse the problem!! I cant come up with anything else. Cheers
The problem is still here:-( the reason it only ran on one sylinder was from cooling fluid spraying over the plug caps(I think) i filled it too much up before testing. After a while it dried off and worked as before. Still struggling with under high load and high rpm. Back to the drawing bord.
I have not synced the carbs yet
and will try new cdi box if it not works after the carb sync. That is about the last things that can possible couse the problem!! I cant come up with anything else. Cheers
12-31-2015, 12:14 AM
#34
Senior Member
SuperBike
Join Date: Mar 2012
Location: New South Wales Australia
Posts: 1,544
These bikes are finicky!
You have to be methodical and try fixes by using the elimination method.
Have you checked the air filter?
Have you checked the resistance of the coils and leads again?
Are the carbs seated properly ?
Are your choke fittings intact?
Are your battery terminals tight?
It could be a lot of other things, however remove the tank, have a good look around, check that the exhaust is sealed and not sucking air.
It is a process of elimination, do one thing at a time otherwise you won't know what the problem is or was .
Good luck.
You have to be methodical and try fixes by using the elimination method.
Have you checked the air filter?
Have you checked the resistance of the coils and leads again?
Are the carbs seated properly ?
Are your choke fittings intact?
Are your battery terminals tight?
It could be a lot of other things, however remove the tank, have a good look around, check that the exhaust is sealed and not sucking air.
It is a process of elimination, do one thing at a time otherwise you won't know what the problem is or was .
Good luck.
12-31-2015, 03:51 AM
#35
Junior Member
Squid
Join Date: Oct 2015
Posts: 8
Working on it:-)
These bikes are finicky!
You have to be methodical and try fixes by using the elimination method.
Have you checked the air filter?
Have you checked the resistance of the coils and leads again?
Are the carbs seated properly ?
Are your choke fittings intact?
Are your battery terminals tight?
It could be a lot of other things, however remove the tank, have a good look around, check that the exhaust is sealed and not sucking air.
It is a process of elimination, do one thing at a time otherwise you won't know what the problem is or was .
Good luck.
You have to be methodical and try fixes by using the elimination method.
Have you checked the air filter?
Have you checked the resistance of the coils and leads again?
Are the carbs seated properly ?
Are your choke fittings intact?
Are your battery terminals tight?
It could be a lot of other things, however remove the tank, have a good look around, check that the exhaust is sealed and not sucking air.
It is a process of elimination, do one thing at a time otherwise you won't know what the problem is or was .
Good luck.
01-21-2016, 07:38 PM
#36
Member
Squid
Join Date: Mar 2010
Location: Poulsbo, WA
Posts: 48
I may suggest checking for any intake leaks (a can of butane), check all over the carbs/intake seating areas. I would also pull the carbs and completely take them down checking the jets and needles for sizing and obstructions. Anything "floating" around can be brought up to a jet when the pressures build. From what you describe I think you have a fueling issue in the carbs. Also if you have access to a dyno and exhaust gas analyzer check the fuel/air ratio at all engine speeds with someone astride the bike.
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