Overheating and Detonation Warning Sighs

JohnSwitch

JohnSwitch

Member
Aug 21, 2011
72
2
34
Stellenbosch, South Africa
I was out riding my blaster today in a part of the world that is extremely sandy and a lot of it is almost like sand dunes. I was riding the quad hard and it had to work hard in the sand. It was a cool day at about 20°C. I have ridden the same track in the dead of summer about 3 months back where the temp was about 35°C plus with no problems. I did not have any problems today but for some reason I have this feeling that the quad was running hot. I am going to recheck my jetting tomorrow just in case.

Can anyone tell me what sort of sign I need to look out for that could be telling me the blaster is running hot. When it runs hot I can expect detonation? I have been told that detonation sounds like coins shaking in a tin cup, is this something that I could miss or would I know right away?

When I stoped I dripped a couple of drops of water onto the fins of the cylinder and they boiled away pretty quick. Is that normal or a sign of overheating?

Any help would be appreciated. I just want to know about the warning sighs.
 
Cooler days require a larger main jet, lower temps need more fuel.

Did you re- jet?

Detonation does sound like you say, but if you were only a little lean you possibly would not hear it over the sound of the motor.

Your best bet is to do a plug chop to see where the jetting is at.

As a rule, whenever I am going to work the motor hard, like in sand or similar, I always bump up the main jet one to help it run cooler.
 
Blaaster said:
Cooler days require a larger main jet, lower temps need more fuel.

Did you re- jet?

Detonation does sound like you say, but if you were only a little lean you possibly would not hear it over the sound of the motor.

Your best bet is to do a plug chop to see where the jetting is at.

As a rule, whenever I am going to work the motor hard, like in sand or similar, I always bump up the main jet one to help it run cooler.
Click to expand...

I did not re-jet. Did not think that that sort of temp difference would effect it so much. When I lasted did a plug chop it was 35deg plus.
What about the water on the fins?
Thanks for the input!
 
right, welcome to the world of OKO carbs!!!!!X(

If you stick your ear about 2cm above your bowl of Kelloggs rice crispies in the morning and hear that snap crackle pop----thats what is sounds like. like a little man in your exhaust with a hammer. if you hear it, its already too late. check that jetting ASAP.

Are you running advanced timing? if so, back it off a tad.

Check out this thread...read the story after the bottom pics...http://www.blasterforum.com/pics-vids-9/ive-got-lovely-bunch-pistons-43480/
 
Hey Blaner

I have not advanced the timing, the guy that built my motor advised against it because of the skimmed head. Will check the jetting first thing tomorrow. Dont want to destroy my motor just yet. Will check the links now thanks!
 
well then id suggest also checking for air leaks via a leak test. id actually do that first!

Just a heads up, something I noticed with that OKO is that the top cap didnt seal airtight with that paperish gasket. this is a problem, because a leaktest doesnt pick that up. I made a rubber gasket instead. Also, i found a leak where the cable fits into the cap, I put heat shrink over the cable to help seal it. All of these flaws on these carbs lead to the hugely variable jetting requirements from carb to carb. Block the one end with your hand, and blow in the other side and spray it with soapy water to see if the carb itself is airtight or not.
 
They sell infared thermometers if you really want to measure your jug temp.

I can tell mines getting hot by the smell. When I ride the sand for a little while the smell of the motor changes.....almost like the paint on the jug is burning. This probably sounds a little wierd, but that's how I can tell.
 
piezzi said:
They sell infared thermometers if you really want to measure your jug temp.

I can tell mines getting hot by the smell. When I ride the sand for a little while the smell of the motor changes.....almost like the paint on the jug is burning. This probably sounds a little wierd, but that's how I can tell.
Click to expand...

Hey Piezzi

I know what you are saying I also noticed the smell!
 
Did the plug test yesterday, attached a photo of the results. The first photo is the plug test from 3 months back in the dead of summer with temps of about 35degC and the second photo is yesterdays test with temp at about 20degC. There have been no change to the jets, airbox or motor. The smoke ring on the two plugs are way different. Any thoughts?

I also looked at the old plug to see if there are any signs of detonation but could not see anything but I dont have a mag glass.
 

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You may not find any signs or detonation on the plug, I have known a motor with a fried piston, show no signs on the plug.

That second plug looks too lean to me.

I wonder if you may have inherited an air leak, may pay to do a test.
 
hard to see that second pic, perhaps you didnt run it WOT long enough? but it definately looks leaner. you need to do a leak test ASAP
 
Not going to do the F to C conversion, but I do know on the Micuni pocket calculator it recomends 1 jet size for every 20*F change. And I know 15*C colder is a lot, that is why it looks lean, because you are
 
Blaner said:
hard to see that second pic, perhaps you didnt run it WOT long enough? but it definately looks leaner. you need to do a leak test ASAP
Click to expand...

I was WOT for about 15s then I ran out of road do you think that is to short?
My first thought when I took a look at the plug was that it is WAY lean. Dont think the temp difference would have made it become that lean if you compare the two photos.

I am not going to do anything till I can do a leak down test.

Thanks for the input guys!
 
Ok I attached a photo of my leak down tester. I will try test the motor this coming weekend. What is a good pressure to test the motor at? I read on the forum that you should test to 15psi(1bar)? Can I test up to say 3bar or is that to high? Can I cause damage with a leak down test at 3bar?
 

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