Don't know what's going on. Brand new engine. Ported cylinder. Slant head. Performance pipe. No signs of air leak. B8HS spark plug. My motor overheats so bad. I had a milled slant head on it. I would ride it for 5 minutes, then I stopped it, spit on the head and cylinder, and they both fried like bacon. Now, I put the stock slant head back, and with stock NT settings (I'm at 5000 ft) it's not as bad, but it still does sizzle a little bit on the cylinder when I spit on it.
Engine Overheating
- Thread starter fischer550
- Start date
I recently had one do this and it turned out to be a bad crank seal.
Ran fine after I replaced the seals. I plan to slap a puch head on this motor soon since the slant heads are very marginal even o0n a mild engine
Ran fine after I replaced the seals. I plan to slap a puch head on this motor soon since the slant heads are very marginal even o0n a mild engine
Mine was overheating so badly it would refuse to shut off due to dieseling!
Be aware the slant heads are very marginal and will run fairly hot even normally...
Maybe borrow a temp gun and check it more carefully?
Be aware the slant heads are very marginal and will run fairly hot even normally...
Maybe borrow a temp gun and check it more carefully?
Seals fixed it right up. Weirdest issue I've ever had in a HT
No other signs on lean mixture. Ran fine until and after cooling off. Plug looked normal.
No other signs on lean mixture. Ran fine until and after cooling off. Plug looked normal.
What you discribe has been the norm for all my china girl engins since the first one I ever run, a head with more mas and good size fins to wick heat away does help the engine run cooler than the stock heads, and especially on engines that have been modified so they produce more power and higher rpms than a stock engine.
Multiple vendor s of after market heads out there and then there is the Puch heads that work good on the china girl 66cc engine after drilling the holes from 6mm to 8mm, or you can buy a custom built aluminum head that will bolt right on like the Fred Chelminski heads which have been proven to be a great addition to other mods because they do allow the engine to get rid of its heat better.
Map
The standard straight fire head is also a good option, although may need to be shaved.
Angle fire head is crap.
Angle fire head is crap.
If sizzling spit is your only indication of "overheating" my advice would be to just ride the bike and quit spitting on it. Any internal combustion engine will get hot enough to evaporate water (saliva). At our altitude water boils at about 190 degrees F. I can guarantee you that the cylinder head and cylinder will exceed that temp.
Tom
Tom
The stock china girl heads whether slant or straight plug type have always worked fine for me on a basically stock engine or slightly modified as long as I ride within reason and dont run all out at max rpm for long distance, I live in a harsh dry and hot climate down here in central Texas so for my high rpm builds lately I have been using heads that have more surface area to draw heat from engine better, but for normal toodling around type riding the stock heads work just fine in my experience and never had a failure that I feel had anything to do with overheating.... shrug mayb a couple blown head gasket could be a result but not sure really...?????
Map
Map
If the motor starts to smoke, it's overheating. Spitting on it will sizzle on any engine, run your lawnmower for 5 minutes and try it.
What kind of 'performace pipe' did you put on it, & what oil ratio are you mixing into the gas??
Also... what kind of oil are you using?
Also... what kind of oil are you using?
Attached is a photo of the pipe (not my bike). Oil ratio 24:1 for break in, using lucas semi-synthetic oil
Attachments
I have one of those expansion pipes on one of my bikes, works pretty good and has good sound, mine is set up on the bike a little different but same chamber.
Lucas makes good products so I'd say you're good on the oil and the ratio for break in, after 2-4 tanks of fuel I'd reduce oil in mix to 32:1 and tune carb for that mix and you should be good to go.
Map
right now I am using a dellorto mock carb because the NT just wasn't doing the job. I have a 65 jet in there now, when I switch to 32:1 should I go bigger or smaller jet?
32:1 is a richer fuel mix, ( more gasoline and lss oil ) you may need to go a size smaller on the jet, but I wouldn't change anything until I knew for a fact that the mix the engine was running on was 32:1 and then I would eirher clean the spark plug really good with carb cleaner spray and a wire brush or replace it and then run the bike up the road a couple miles and back, let it sit for about 10-15 min to cool some and then pull the spark ug and see what color it is, if it dark brown or close to a blackish color thats a sign the jet is a bit large and causing a rich run on fuel, you'll also know by how it runs of course, if it blubbers a lot under thottle you'll also know right off its running to rich on fuel, @ 15-20 mph and up and under cruise speed throttle it should have an even buzz soud and not the blubbering sound which indicates its 4 stroking.
If you do reduce main jet size be sure to clean plug and do another plug chop to make sure the plug isn't running white which will indicate a lean condition and will, cause the engine to run to hot and cook it. In a short amount of time, that light chocolate tanish brown color is what I look to achieve and zero to little 4 stroking at medium to upper throttle and cruise speeds.
If Im preaching to the choir hear forgive me, just being thorough with my explanation of how I get my jetting where I want it for best all around performance.
Best wishes
Map
