Won't rev above 7k, carbs or coils?

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Alex.
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Won't rev above 7k, carbs or coils?

Post by Alex. »

Bit of background info, I bought my Storm a few months ago with standard cans and 7 year old touring tyres. It also came with a pair of race cans and the appropriate jets. These jets had been removed when the standard cans had been put back on, to reduce the noise for neighbours and early starts. It had been standing for a couple of years, due to various personal issues of the previous owner.
I rode the bike a couple of times, but the tyres were always in the back of my mind, so I didn't explore the performance. When I changed the tyres, I also did a service, changed the cans and jets. Next time I rode the bike it would not rev above 7k, just like hitting a brick wall the engine just would not spin faster. The carbs came off (eventually) and given a thorough cleaning, this made no difference. She did not like to rev over 7k just sitting outside the garage, so under no load.

Yesterday I put the standard jets and cans back on and now the revs would go all the way to the red line without a hitch or complaint. Game on I thought!

Riding to work this morning, she still does not like reving above 7k, but now it is only a reluctance with little extra acceleration, rather than a brick wall.

I had been thinking it could be the coils, but now not too sure. If it was the coils, I would expect the cans to make no difference. Could the carbs need a more thorough ultrasonic cleaning?

What say you, oh knowledgeable peeps? Coils? Carbs? some other part beginning with C...

Alex.
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AMCQ46
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Re: Won't rev above 7k, carbs or coils?

Post by AMCQ46 »

easy.......... your cam timing is out by 180degrees and the intake system cant flow enough air for the engine running in "big bang" timing with the intake pulses are too close together

have a look through workshop section
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Alex.
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Re: Won't rev above 7k, carbs or coils?

Post by Alex. »

AMCQ46 wrote:easy.......... your cam timing is out by 180degrees
I knew that one was coming... I have every confidence in the previous owner and the maintenance carried out to this bike, that it is not the cam timing. I have know the previous owner for years and trust his riding abilities. If the cam timing was out, he would have noticed it on the first ride out of the shop and it would have been corrected.

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Wicky
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Re: Won't rev above 7k, carbs or coils?

Post by Wicky »

So to summarise - the previous owner when he last rode it never had a problem @7K - You bought it and rode it a couple of times without a problem then suddenly out the blue it hit a brick wall.

Did the PO ever have CCT failure (hence why it was laid up)? In your initial couple of rides did you get it over 7K?

What about the airfilter?
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Alex.
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Re: Won't rev above 7k, carbs or coils?

Post by Alex. »

Wicky wrote:So to summarise - the previous owner when he last rode it never had a problem @7K - You bought it and rode it a couple of times without a problem then suddenly out the blue it hit a brick wall.
Almost. In my first couple of rides, I did not go above 7k as I had no faith in the old tyres and I was just pootling about. After I changed the tyres and cans, I ventured north of 7k, or tried to.
Wicky wrote:Did the PO ever have CCT failure (hence why it was laid up)? In your initial couple of rides did you get it over 7K?
There was a CCT failure many years in the past, which was fixed long before the lay up. The previous previous owner (previous owners now deceased son) would definitely have noticed and fixed a timing issue then.
Wicky wrote:What about the airfilter?
The air filter is a K&N, which was cleaned and oiled at the same time as a carb clean.

I'm still suspicious of the coils, as they could have degraded during the inactive years.

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AMCQ46
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Re: Won't rev above 7k, carbs or coils?

Post by AMCQ46 »

over oiled K&N could be a problem, but I would still check the Cam timing just to rule it out
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Wicky
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Re: Won't rev above 7k, carbs or coils?

Post by Wicky »

So as far as you know the problem was latent from the PO - Whatever you think of their spannery skills and due to fact that it has had CCT failure in the past which would be the most oppurtune time for the er.. timing to have been done wrong - it would be definitely worth your while (and it'll be free!) to investigate and rule out the timing.

Did they fit manuals after the CCT failure?

Revving to 7k then flat
Recently I changed my CCT's to manuals and when removing the one on the rear cylinder it slipped meaning i had to reset the cams. Well I managed to rock up basically and set the 180o out. Meaning when it was ridden:

It sounded boomy/hollow
Revved / revs to 7k then stops like it's hit a limiter (about 100mph)
....
Whip the cams out and reset properly, and it's fine
rough running
After having his vtr into the dealer with the dreaded cct failure my mate says since he got it back it won't rev past 7k
...
i told him how to check the timing himself and suprise suprise it was 180 degrees out
180 out?
The Bike runs great except one thing. It pulls strongly, when she reaches 5-5500 rpm has an outbreak but then doesn't pull strongly till limiter.

I simply cannot rev it with 2nd gear till the limiter like a Firestorm.
.....
Finally I fixed my beauty!!! Its was 180 degrees out!! Oh mygod now I own a different bike!! The sound, the acceleration the smooth ride!!
Last edited by Wicky on Tue Aug 30, 2016 3:50 pm, edited 2 times in total.
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Wicky
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Re: Won't rev above 7k, carbs or coils?

Post by Wicky »

+1
AMCQ46 wrote:over oiled K&N could be a problem, but I would still check the Cam timing just to rule it out
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Alex.
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Re: Won't rev above 7k, carbs or coils?

Post by Alex. »

Wicky wrote:So as far as you know the problem was latent from the PO - Whatever you think of their spannery skills and due to fact that it has had CCT failure in the past which would be the most oppurtune time for the er.. timing to have been done wrong - it would be definitely worth your while (and it'll be free!) to investigate and rule out the timing.

Did they fit manuals after the CCT failure?
I will be checking the timing, but as garage time is limited I was looking for further suggestions to investigate.
The CCTs were replaced with standard. This was long before I took ownership and would have been picked up and corrected very soon after.

Alex.
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Re: Won't rev above 7k, carbs or coils?

Post by Alex. »

AMCQ46 wrote:over oiled K&N could be a problem, but I would still check the Cam timing just to rule it out
If the filter is over oiled, how would I un-oil it? Using the K&N cleaning stuff?

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Re: Won't rev above 7k, carbs or coils?

Post by Wicky »

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eamonn
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Re: Won't rev above 7k, carbs or coils?

Post by eamonn »

Basic stuff, are you getting full throttle, operate the throttle butterfly's manually, therefore eliminating the throttle cable ?
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Re: Won't rev above 7k, carbs or coils?

Post by sirch345 »

AMCQ46 wrote:over oiled K&N could be a problem, but I would still check the Cam timing just to rule it out
+2

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agentpineapple
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Re: Won't rev above 7k, carbs or coils?

Post by agentpineapple »

speaking from experience, I bought my first vtr about 6yrs ago, it was my first twin, so I had nothing to compare it to. I loved it, but there was a slight hesitation around the 6.5/7k region, then it would continue to rev out to 9k.
so a friend helped me with some carb work, but everything we tried made it worse, even tho we knew what we had done should have improved things.
I dismissed the timing being out, because when I first bought it, it revved to 9k, when i'd red that if the timings out it won't rev past 7k.
in the end we checked the timing, and it was out by 180.
once we sorted the timing, the bike was at full power, and I had the biggest grin ever.
so my point is, don't discount the timing being 180 out.
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agentpineapple
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Re: Won't rev above 7k, carbs or coils?

Post by agentpineapple »

one other possibility is a tear in the diaphragm of the petcock, take it apart and check, just remember how to put the bugger back together again
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