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Discussion Starter #1
So I've seen two different schools of thought on the glowing cherry of the exhaust header on air/oil cooled King Quad 300F. One is that it's normal on an air/oil cooled design like this when sitting idle or moving slow and the other that it's too hot by being too lean and needs the pilot/mix screw turned out to richen the mixture. What is the hard facts about this issue really? Lol.
 

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It's both......But mainly running lean ( all air cooled will heat up if not moving especially it hot weather)

Most common reason is that the idle circuit jet is blocked to some degree......
 

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Discussion Starter #3
Ok. I guess I'll try backing the pilot screw off a little after I try to determine how far out it already is.
 

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If the jet is blocked......that's not going to fix the problem ( might help some for a while)
 

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Discussion Starter #5
Right. I wouldn't think it was blocked so much since I had it cleaned/rebuilt a while ago and a fuel filter put on at the same time. It runs pretty good even now but I'll monitor it nevertheless.
 

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If it is a CV type carb, it is an air screw, (before the slide) so backing off leans it out more.

Regular carbs the screw is a fuel screw, back out to add fuel.

Easiest way to tell the difference between a CV and a normal carb is the throttle cable controls a butterfly valve on CV carbs, it controls the slide on regular.

Not sure what years Suzuki used the CV carb on, but my 1990 has one, but the 1989 does not.
 

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Definately not normal. Usually when running lean the engine will miss badly especially under load. The idle mixture screw only controls the mixture at idle. The main jet controls the mixture above engine idle speeds. At least two other possibilities exist: vaccum leak, & burnt exhaust valve. The rubber flex intake manifolds are notorious for leaking against the head. I've sucessfully used RTV silicone to seal these. You can test for a leak by spraying carb cleaner around the base at the head with the motor at idle. If it speeds up the engine is drawing in the added fuel via the leak. Let's not talk about the burnt valve. It's bad news.
Happy diagnosing!
 

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As an aside I just bought a complete new carb on eBay for under
$40 for a 2001 300 Quad runner. Cheaper than messing with rebuilding one!
 

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Discussion Starter #13
I reported my findings on another thread but want to here also. It turns out the geniuses at the shop had left my pilot screw fully seated. No wonder the header turned red and the idle sucked. I got it turned out about 2 5/8 as the repair manual states and I'll start it up later.
 

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Discussion Starter #14
Looks like she's running pretty good now. I can't fine tune the pilot screw obviously but she's not spitting and idling like a nutjob anymore. Also I didn't notice any glow at the header. I didn't have it sitting for a long time and idling but I'm going to guess that it's fine now. At least for the design. Only issue was the plug bolt on the lower right side of the muffler/spark arrestor wanted to come out since it wasn't locking into place but after it warmed up it seemed to be alright after tightening it by hand again.
 
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