Flooded 670

RB670 · Jan 21, 2019

Hi all. I have a new to me 1996 670 mxz. It has a new engine. I tried it out on the weekend and had crazy excessive fueling issues.
My question is the jetting. I don't go to the mountains at all. What is the correct jetting for this engine?
This thing flooded to the point where I had to shut the fuel off and pull it until it started at WOT. Anytime I gave it more gas(turned fuel back on) it would flood out.
Was thinking maybe bad fuel pump too...can it suck into the engine from the vacuum feed?

Any help would be great

Richard

team dirt · Jan 21, 2019

Float levels are to hi. Take carbs out pull bowl covers. Flip carbs upside down and see where the floats sit on the spring tension on the seat and needle. There’s a little brass tab you can bend to raise or lower the floats. The arm that brass tab is on should be roughly level with just gravity pulling down against the spring tension. Also check the seat and needle for tight seal. If they are leaking it will cause flooding. Mark the carbs before pulling as jetting is different from mag to PTO due to the rotary valve.

RB670 · Jan 21, 2019

I will double check that, Thanks!

roughriders · Jan 21, 2019

yes check what team dirt said, these carbs also sit at quite a bit of angle which doesnt help the floats . they are touchy

KatMan · Jan 21, 2019

even just a good cleaning of the floats. they may have been stuck open.(down)

you can adjust full close on the valve by slightly bending the point where the float arm hits the needle. you'll see what i mean when yo take it apart.

bend it in the direction of the needle to stop the fuel to the bowl sooner. there will be a small mark(dot) on the side that hits the needle.

snopro · Jan 21, 2019

Don't rule out the primer being buggered and allowing fuel to flow into the carbs as well. That is a common issue as well to look at. Chances are the carbs weren't touched in the rebuild on the motor so rotary valve timing could be wrong if the tech didn't know what he was doing if it was a back yarder. If everything else checks out good I would look at that as well. Good luck!

Bogger · Jan 21, 2019

AND never park a 670 facing downhill........

pfi572 · Jan 21, 2019

Bogger said:
AND never park a 670 facing downhill........

Shut fuel off of for above or you have to roll it over for some reason .
Have seen it so bad guys would be pulling them out . Couldn’t get started . We would just pull plugs and tip up-side down to drain fuel out of cylinders . Lol
Guys would be yeh whatever.
Tip back over with dry plugs and fire it right up .

0neoldfart · Jan 21, 2019

Most of the 670’s carbs (both 40 & 44mm) had Viton needle and seat. A good fix to prevent flooding when pointed downhill was to use the heavier brass units from the 94? Mach 1.

RB670 · Jan 22, 2019

Floats are set properly. I pulled all the fuel out suspecting maybe bad fuel(water in fuel?) One thing I noticed is that there was what looked like brass filings in the bottom of the tank. Cleaned everything out and installed a fuel filter. Turned the fuel on and pulled over. Almost instantly, the carbs flooded. Fuel was actually pooling inside the carb.
My suspicion is bad fuel pump,over pressuring the system...Thoughts?

MK4TDI · Jan 22, 2019

RB670 said:
Floats are set properly. I pulled all the fuel out suspecting maybe bad fuel(water in fuel?) One thing I noticed is that there was what looked like brass filings in the bottom of the tank. Cleaned everything out and installed a fuel filter. Turned the fuel on and pulled over. Almost instantly, the carbs flooded. Fuel was actually pooling inside the carb.
My suspicion is bad fuel pump,over pressuring the system...Thoughts?

Friend had a 670 that , we replaced the needle and seats on his with new and everything went back to normal.

RB670 · Jan 24, 2019

Replaced needles and seats=same issue

MK4TDI · Jan 24, 2019

Fuel pump also acts like a check valve on that system if I remember correctly. The only other thing holding fuel back is the needle and seat and the on/off valve. I would change out the fuel pump or at least find a service manual to see if there is a way to perform a test on it.

snopro · Jan 24, 2019

Did you check if fuel was syphoning through your primer yet?

Flooded 670

RB670

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team dirt

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RB670

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roughriders

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KatMan

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snopro

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Bogger

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pfi572

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0neoldfart

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RB670

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MK4TDI

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RB670

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MK4TDI

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snopro

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