single carb 340 fouling pto plug

RMK-King

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Dec 25, 2007

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• Mar 12, 2015

• #1

I have a yamaha ovation 340 with a single 34mm mikuni carb, oil injection has been removed. The sled wants to foul the pto plug,it seems to be the worst at full throttle. The mag plug is always nice and dry. I have tried switching plug wires around with no change. 100psi in both cylinders. Bad crank seal would should cause that cylinder to run lean not? Fuel pump pulse line didn't have any gas in it. I don't know what else it could be.

 

R

retiredpop

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• Mar 17, 2015

• #2

The original carb on those had kind of an unusual intake setup with almost a dual output to the intake manifold.
http://www.yamahapartspitstop.com/oemparts/a/yam/5003bc89f8700212fc8400e1/carburetor

http://www.yamahapartspitstop.com/oemparts/a/yam/5003bc89f8700212fc8400e0/intake

Perhaps it provided for a slightly leaner flow to the pto side and now you are providing equal flow to both sides. Just a thought though as I don't really know. When yours was converted to the Mikuni did you (or they) use a different manifold than the stock? I would be inclined to check for an air leak on the mag side rather than look at the pto side. If everything checks out perhaps you could try running a BR8ES plug which is one heat range hotter on the pto side and watch it closely until you get a good handle on it.

 

Last edited: Mar 17, 2015

S

stingray719

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Jan 22, 2008

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stingraymods.com

• Mar 17, 2015

• #3

Sledmax said:

I have a yamaha ovation 340 with a single 34mm mikuni carb, oil injection has been removed. The sled wants to foul the pto plug,it seems to be the worst at full throttle. The mag plug is always nice and dry. I have tried switching plug wires around with no change. 100psi in both cylinders. Bad crank seal would should cause that cylinder to run lean not? Fuel pump pulse line didn't have any gas in it. I don't know what else it could be.

Click to expand...

Is that a reed valve engine?

 

RMK-King

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• Mar 17, 2015

• #4

I converted it myself recently,it ran worse with the original 2 barrel carb. I used a intake from a enticer which is the exact same engine so adding this intake shouldn't be causing any issues. There is no reeds on this engine.

 

A

Aerosled

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• Mar 17, 2015

• #5

Here's a short video on mounting a single carb on a twin. Its a Rotax with a bing carb but same principle as a mikuni.

http://bcove.me/lfkg1kem

 

Last edited: Mar 17, 2015

R

retiredpop

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• Mar 17, 2015

• #6

Aerosled said:

Here's a short video on mounting a single carb on a twin. Its a Rotax with a bing carb but same principle as a mikuni.

http://bcove.me/lfkg1kem

Click to expand...

Good find! Who would have thought that would make a difference but it does make sense.