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Discussion Starter · #1 ·
I have a freshly rebuilt 400ex with a 416 bore, weisco 10:1 piston, and stage 2 hotcam. I was breaking it in and noticed that when testing the temp with an Infared Thermometer on the cylinder, the temp had climbed to 250 degrees after just fifteen minutes of putting around. I could be wrong, but that seems way too hot, what could be causing this?
 

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Jetting! 250 isnt way to hot. But it is hotter then i would feel comfortable with unless your riding in the sand dunes. My quad runs around 200 normal and hit 230 once at the dunes. I run a 4 inch dust proof and water proof spal fan on my oil cooler and it brought temps down quite a bit. Those and air shrouds help to. Welcome to the forums!
 

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Jet kits are a waste of money. You can do the samething a jet kit can for 1/3 the price with individual jets. If you cant find a local shop to sell them go to jetsRus. Give me all your mods. Every last one. And i will give u a base to start with!
 

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Discussion Starter · #5 ·
alright I have the 416 bore with 87mm 10:1 piston and a stage two hotcam, FMF power bomb header with DG slip on, and a UNI air filter.
 

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Ok i would start with a 42 pilot jet. Mixture screw around 2 1/4-2 1/2. And 175-180 main jet. With needle clip(if adjustable) in middle position.
 

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No problem! Always glad to help! Keep us posted
 

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An over-sized oil tank can help too as it lets the oil cool longer before being returned to the motor.

Start with jets, and if it's still running hot, try some shrouds, a fan, or bigger oil tank.
 

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Discussion Starter · #13 ·
Ok almost positive it's a jetting issue due to the fact that when I get past half throttle it cuts out, although I may invest in spal fan also
 

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Jetting! 250 isnt way to hot. But it is hotter then i would feel comfortable with unless your riding in the sand dunes. My quad runs around 200 normal and hit 230 once at the dunes. I run a 4 inch dust proof and water proof spal fan on my oil cooler and it brought temps down quite a bit. Those and air shrouds help to. Welcome to the forums!
Pics of your fan I run the dunes too. I'm thinking about adding those bigger eBay oil coolers

Sent from my SM-G920V using Tapatalk
 
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