high RPM misfire

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tastethefloor
Posts: 117
Joined: Wed Oct 26, 2016 8:45 am
Location: Modena (Italy)

high RPM misfire

Post by tastethefloor »

Hi, I had posted this problem also on facebook group, i try here maybe people on the forum is more prepared...
my bike has develop a high rpm misfiring above 7500 8000 rpm, she like hittng the limiter and the restart to pull without problems to redline...
I had swap with another vtr this parts but the problem persist..
- COILS
- PLUGS
- PLUG CAPS
- HT CABLES
- CDI (BOTH)
- PULSE GENERATOR 8O 8O
I had check all the connections, cleaning accurately the carbs, double check the timing, compression
everything is ok
what should I do? thank u in advance
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MacV2
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Location: Grain

Re: high RPM misfire

Post by MacV2 »

Check the petcock diaphragm...split or hole will get bigger under the increased vacume, cutting fule...
Making up since 2007, sometimes it's true...Honest...
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tastethefloor
Posts: 117
Joined: Wed Oct 26, 2016 8:45 am
Location: Modena (Italy)

Re: high RPM misfire

Post by tastethefloor »

also checked it, is ok
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MacV2
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Re: high RPM misfire

Post by MacV2 »

tastethefloor wrote: ↑Thu Jan 17, 2019 3:32 pm also checked it, is ok
You running std air filter, std cans...early or late bike ..ie does it have PAIRS system on it...?
Making up since 2007, sometimes it's true...Honest...
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tastethefloor
Posts: 117
Joined: Wed Oct 26, 2016 8:45 am
Location: Modena (Italy)

Re: high RPM misfire

Post by tastethefloor »

yes all standard, PAIR still on
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MacV2
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Re: high RPM misfire

Post by MacV2 »

tastethefloor wrote: ↑Thu Jan 17, 2019 3:52 pm yes all standard, PAIR still on
Take the PAIRS off...
Making up since 2007, sometimes it's true...Honest...
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tastethefloor
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Re: high RPM misfire

Post by tastethefloor »

sorry why? I'm confused :eek2
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MacV2
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Re: high RPM misfire

Post by MacV2 »

tastethefloor wrote: ↑Thu Jan 17, 2019 4:06 pm sorry why? I'm confused :eek2

PAIR system is a air clean system that recycles some of the fumes & nasty stuff from the cam boxes & sends it back through the air box...Thanks to our Californian chums all US bikes had it fitted...& I suppose to save a bit of money on not having to do two or more different versions we all got lumberd with it... Easy enough to take off & hurl in the nearset bin... Either buy a PAIR deleat kit... viewtopic.php?f=38&t=42705 ... or flip the valves on the cam covers & cap off all the hoses... or change cam covers for early ones & change the air box base...
Making up since 2007, sometimes it's true...Honest...
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tastethefloor
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Joined: Wed Oct 26, 2016 8:45 am
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Re: high RPM misfire

Post by tastethefloor »

:thumbdown: Not related to my bike problem
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StormyRob
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Re: high RPM misfire

Post by StormyRob »

tastethefloor wrote: ↑Thu Jan 17, 2019 5:55 pm :thumbdown: Not related to my bike problem

This was not a great reply. He was trying to assist. 😂
If you don't try you never know if you can do it.
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tastethefloor
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Re: high RPM misfire

Post by tastethefloor »

:clap:
Now u feel better?
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Wicky
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Re: high RPM misfire

Post by Wicky »

Check carb intake rubbers are nice and sealed - same for any exhaust leaks i.e. manifold/header/link pipes. Check vacuum hose isn't split and correctly attached.

And bin the PAIR system :p

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Chris58
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Re: high RPM misfire

Post by Chris58 »

I know that coils like to do that at high rpm when they are failing... They will work fine at lower rpm, but as you put more load on them (rpm) they will cause a misfire... but i see you checked that.

Also does sound like it could be a fueling problem... Most petcocks have a screen filter inside the tank that can get clogged up..or the diaphram doesnt work. its happened to me twice on different bikes with the exact same symptoms.
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tony.mon
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Re: high RPM misfire

Post by tony.mon »

Have you changed the cct's lately?
It's not falling off, it's an upgrade opportunity.
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tastethefloor
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Joined: Wed Oct 26, 2016 8:45 am
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Re: high RPM misfire

Post by tastethefloor »

Chris58 wrote: ↑Thu Jan 17, 2019 8:32 pm I know that coils like to do that at high rpm when they are failing... They will work fine at lower rpm, but as you put more load on them (rpm) they will cause a misfire... but i see you checked that.

Also does sound like it could be a fueling problem... Most petcocks have a screen filter inside the tank that can get clogged up..or the diaphram doesnt work. its happened to me twice on different bikes with the exact same symptoms.
This is a good reply.thank u
I don t really have a method to test them at high rpm on the bench
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