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Recently developed low rev miss

Old 01-14-2013, 07:37 PM
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Recently developed low rev miss

Guys (and gals) need some leads here. My 2000 vtr has recently developed a low speed miss, akin to a bucking bronco!.

Seems to happen with a load on up to around 3000rpm and I have done no changes/mods to the bike that would explain this. New spark plugs have made no difference nor having the carbs checked/balanced. Appears more frequent when up to operating temp. This is not just a small miss but when accelerating will miss several times before getting over the 3000rpm mark hence my "bucking bronco" comparison.


(Slightly off topic, I have done a few track days and the bike would always drop down to one cylinder after braking hard and dropping into a very tight left hand corner - any suggestions? Less concerned about this as I have a Daytona 675 for track days these days but interested in your thoughts never the less.)

Cheers
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Old 01-14-2013, 08:07 PM
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It is a pilot jet problem. Clean them or replace them and the problem should go away. Yes I also recommend going up one size on the pilots to #48s

For the braking stumble, check the float bowl vent lines, it was more of an issue on the earlier models but the fix is to take the vent lines from where they cross in the middle of the carb stays and pull them out and route them pointing down on the outside of the stays and you should be good to go.
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Old 01-14-2013, 11:55 PM
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Thanks 8541Hawke and VTRsurfer, I appreciate the advise. Will look to source the #48 pilot jets.

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Old 01-15-2013, 12:59 AM
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Any recomendations as to where to buy the jets from?
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Old 01-15-2013, 01:41 AM
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Motorcycle dealers / carb specialist shop / online
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Old 01-15-2013, 06:17 AM
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You can also try ebay, they go for about $5 over here in the states, though I didn't see anything on Aussi/NZ ebay... maybe they will be willing to send them your way from here? Online definitely easier to find the 48 jets I reckon, unless you got a shop close to you that may have these, even used jets would do.
Good luck mate
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Old 01-15-2013, 07:41 AM
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They are common for many different carbeurated bikes. More often dirt bike shops have them. You're looking for Keihin Series 21 pilot jets, Size 48.
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Old 01-15-2013, 11:21 AM
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Originally Posted by 7moore7 View Post
They are common for many different carbeurated bikes. More often dirt bike shops have them. You're looking for Keihin Series 21 pilot jets, Size 48.
Thanks 7moore7, thats also a great help.

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Old 01-16-2013, 04:01 PM
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Originally Posted by stormy1 View Post
Guys (and gals) need some leads here. My 2000 vtr has recently developed a low speed miss, akin to a bucking bronco!.

Seems to happen with a load on up to around 3000rpm and I have done no changes/mods to the bike that would explain this. New spark plugs have made no difference nor having the carbs checked/balanced. Appears more frequent when up to operating temp. This is not just a small miss but when accelerating will miss several times before getting over the 3000rpm mark hence my "bucking bronco" comparison.


(Slightly off topic, I have done a few track days and the bike would always drop down to one cylinder after braking hard and dropping into a very tight left hand corner - any suggestions? Less concerned about this as I have a Daytona 675 for track days these days but interested in your thoughts never the less.)

Cheers
stormy1
I had a similar issue. Between 3000 and 4000 rpm in 1st and 2nd gear my bike hiccuped and hitched a bit. Drove me nuts! I went and re-synced the carbs and my little problem seems to have left me. Hawks carb set up is next on my list.
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Old 01-29-2013, 11:32 PM
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Well I pulled the carbs off and replaced the pilot jets with new #48's and took the opportunity to re-route the vent lines. Regret to say the missing problem is still there
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