What are your jet sizes?

496 BB

New member
So Im running the 14cc head and flattop piston .010 in the hole. BP2 cam with 1.3 rocker on intake. Stock carb bored to around .650. Last couple weeks this thing screams early on then falls flat later in race. Not sure if kart is tightening up but think not since it still handles same. Maybe air pressures I dont know. Anyways I was thinking could it be the motor getting too warm? I know guys say they like to run hot but mine seems to like cooler. I dont know what temps are but am just gauging from performance. Outside of motor temps are consistent each time I check even though I know that is not same as combustion chamber temps.

I jetted main up to a 39 from a 38 last weekend. Did not tell any difference nor did I check plug...(was in a hurry). Low side is still at 24. Running Cam 2 leaded fuel. Should I go up yet another to try to cool motor? I think it personally likes lean. Is lowside too high you think?

Wondering if this is consistent with others are running with similar builds or if I should start looking elsewhere. We run like 30-40 laps at a time on 1/10 mile dirt track. No sanctioning.
 
What springs are you using? still sounds tight or gear bound
The other thing you can do is try a 20 lap feature race
and a 10 lap heat race and see if there is a change.
as for the heat hard to say if you have no way to tell.
but they do make more power if run a little hot.
 
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496 BB

New member
Brand new 26 lbs springs. 11/73 gearset. Not wrapping out on straights as they are short as can be.
 

BradH

New member
Did you jet "up" from a 39 to a 38? May be a typo... but the engine will typically run warmer with a smaller jet. If you want to cool it then add fuel. Your motor will like lean, but your wallet will not! What kind of plug are you using? Any idea of the heat range? Compression ratio with that setup is about 13.3:1. Things get touchy when dealing with that CR. Timing, plug heat range, air/fuel ratio can make or break the performance and longevity. Maybe the best investment would be in a tach that you could get an idea of your head temp. I would suggest running alky too. You may not make as much horsepower as you are currently with gas, but torque will be up and tuning will be way more forgiving with alcohol. JMO. Give us some more specs if you can.
 

496 BB

New member
Leaded is only 110 fuel around here I found. Unleaded is 100. Timing is per cam card and at 30*. Plug is 3910x. I had a 38 and went to a 39 jet. Motor never skips a beat. I would assume if it was too hot it would blow a head gasket which Im running a .010 vinton coated type. I know I need a tach but its not in budget this season. Last race is this weekend and was just wondering about this. As I said I dont know if its the motor or the chassis. Just wanted to see if say a .040 main was way too much for this setup. Also what about low side being .024? Too small too big? If Im within what others have ran successfully then I will look at chassis and tires.
 

Racer14sl

New member
For 110 leaded gasoline, I think your pilot is too big. Try a .020 or .021 and go back to the .038 main jet.

Also, a 11/73 gearset seems like a lot for a 1/10 mile...Unless your racing on a flat paper clip where you nearly have to come to a stop in the center of the turns.
 

Smowkin Joe

New member
For 110 leaded gasoline, I think your pilot is too big. Try a .020 or .021 and go back to the .038 main jet.

Also, a 11/73 gearset seems like a lot for a 1/10 mile...Unless your racing on a flat paper clip where you nearly have to come to a stop in the center of the turns.
This is close to where I started. I have a very similar build, and found mine likes a 21 and 41. I also agree that the gearing seems too high.
 

496 BB

New member
Gearing is just fine for the track. Its tight corners with no banking. It may be smaller than 1/10 mile. Just a guess. Its not any sanctioned event. Home made track but very nice at that. I will have to get some pics someday. Hard to explain. Your on brake more than throttle. Think Nascar and Bristol for Karts.

I will try smaller low side jet. Valve lash cold is .003. I tried .002 this time and may even go .002 warm. With this gearset we are not even reaching full potential of powerband. Still pulling at 6800 when having to brake.

Ring gap was around .006-.007 when installed month ago.
 
Gearing is just fine for the track. Its tight corners with no banking. It may be smaller than 1/10 mile. Just a guess. Its not any sanctioned event. Home made track but very nice at that. I will have to get some pics someday. Hard to explain. Your on brake more than throttle. Think Nascar and Bristol for Karts.

I will try smaller low side jet. Valve lash cold is .003. I tried .002 this time and may even go .002 warm. With this gearset we are not even reaching full potential of powerband. Still pulling at 6800 when having to brake.

Ring gap was around .006-.007 when installed month ago.
.002 lash warm will probably be 0 cold. I would set the lash as close to zero as possible cold. Are you taping the blower housing? What oil are you running? Meth would be better too.
 

496 BB

New member
I did tape the blower housing once. Did it then as well. Its cold outside when we race now. Around 40*. Should I worry about engine getting hot when its this cold? Still tape blower? Im running RedLine synthetic racing oil 20wt. Should I change?
 
Some of my friends ran Thor light on our track when we started. They would run laps and start slowing down. They could change the oil and go back to the faster laps. They went to a thicker oil (like I was running already) and didn't have any problems after that. I don't run thin oils in a higher HP engine. How many laps are you running at a time, and how often are you changing the oil?
 

496 BB

New member
Change oil about every 4 races. Run maybe a total of 60 laps a weekend. What can I get around town that is good? Jegs is not super far away. What weight are you running?
 
Just to be clear, your running 4 race nights, and 60 laps per night on one oil change? I would change it at least after each night, and I run Thor heavy (16oz).
 

496 BB

New member
Recently I havent with everything Ive done to do it. Id say every other race for last month. I got some Redline 30wt today. Think that would be ok?
 
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