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Discussion Starter · #1 ·
I have an '07 660 that I have been running a turbo on and am now going back to stock except for the cam from a Raptor. Put the stock carb back on but it will not run correctly. When I first got it going, it was running extremely rich. Found that the needle had crud under it and was not closing all the way. Now, it is running very lean. Have gone to a 45 pilot jet (40 is stock) and have gone from a 152.5 main (150 is stock) up to a 175 and it is still lean. I can pull the choke out just a little and it will richen up and run more like it is supposed to. I have changed the exhaust thinking maybe it may be the problem but it didn't help. The only thing else that I can think of is changeing the position of the needle. I have played with it some but have not hit on the problem. With the turbo, I had to add several washers to raise the needle but have put it back to the stock position without any luck. I am running out of ideas. Considering going to a 195 main today and working backwards. Any ideas would be greatly appreciated. :aargh4:
 

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how do you know its for sure lean? have you check the plug?

What exhaust? what intake? a 175 should be too rich, not lean....and a 152.5 is too lean...lean and rich conditions can feel the same
 

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On a stock machine, 175 is waaay too rich. In fact, Im running a 157.5 on my 686/port/polish build, so stock should be around that or less. Any chance you can find another stock carb and try that to isolate the problem?

I'd be surprised if it even RAN with a 195 main!
 

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Discussion Starter · #4 ·
Thanks for the feedback.
Plugs are blistering. FMF exhaust. Stock manifold, bore. Only mod other than the exhaust is CDI (run it and FMF for 4 years), and a raptor cam. I agree, a 175 should be much to rich but it isn't. I even have to pull the choke out some to get it to rev up like it should. Don't know anyone with a carb. Going to pull it back down this afternoon and see if I messed up aligning the decompression pins on the cam. Will go back with the stock cam. This thing has been a pain in the butt ever since I tried to make it run with the turbo. Went through two pistons with it and have had enough. Should have listened to Chris at Benchmark in the beginning! Going back to pretty much stock. At least I should have some dependability. Thanks.
 

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yup my well tune stocker runs pretty dam good.

check all the orifices on the cab also, check the diaphragm for pin holes.

did you go from a 152 to a 175? or try each one in between?
 

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How do you know you don't have a fuel delivery problem...

I doubt if it is the cam.... stg1 or stg2 cam will have little or no effect on jetting...neither will porting...

Air intake, exhaust, temperature, elevation... in that order...

Has your slide spring and/or slide been modified or changed...

You haven't mentioned your air intake...if it is bone stock for your year model that is way too restrictive for making it run right with a high flow exhaust...

A 45 pilot jet is a safe bet...you you may be able to make better power with a bigger one but it is not going to be lean or rich...for that pilot jet with no a/f gauge set the idle a/f screw at 2 turns out...

The stock main jet for your year model is a 145 not a 150...not that it matters...

By "blistering" do you mean the electrode is blued and bare metal with no deposits able to collect...

If so it sounds like you could have a vacuum leak...that would have similar symptoms to weak fuel delivery only worse as it would run longer and more reliably and still be way too lean...if fuel delivery was the problem it would have more of a tendency to stall, pop, back fire...

First thing to do always is make sure fuel delivery is good...and go from there...

Stock intake with good exhaust (don't know if your is good or not) if everything else is right in moderate temperatures at sea level would probably need something close to a 157.5 mikuni main jet...

Don't ask dbestduner who beat him with a 2x4 until he got his right... :13:
 

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Discussion Starter · #7 ·
I found the problem. Thanks for everyone's input. All are good suggestions. Tore it back down to the cam and gave everything a close inspection and found that one of the counter weights on the decompression setup was not working and it was holding one of the exhaust valves open. You could turn the engine over slowly and watch the little pin on the cam come around and open the valve but the pin would never retract back into the cam and kept the exhaust valve open all the time. I had bent one of the metal tabs where the bolt goes through it that hold the gear on the cam. It was bent just enough that it wold not let one of the weights move when the engine was turned. A little tweaking with a pair of pliers straighten it out and all was well. Thanks again. What a great forum.
 
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