Heat issues

Risingsunn · Apr 27, 2013

Good afternoon all,
Today I decided to reattach my SBP pipe to my fairly new motor (roughly 200 miles). Once I got the pipe back on, I took it out for a quick test drive. She ran very well and the pipe added the expected perfomance, but WOW was she hot! I've already done heat damage to one good engine and don't want to do it again.
I have lowered adjusted the needle to be richer (yes I know that it doesn't affect WOT) I put in a NKG B8HS for a little cooler spark to see if that would help, but no. I am running about 32:1 Homelite mix which worked well with the stock pipe.
Now I don't have anyway of measuring temps but I do know that when the intake is hot to the touch and the bowl is getting warm enough to make the fuel bubble up the fuel line, then the engine is getting too hot!
Does anyone have any recommendations on how to keep the engine cool? I would really like to be able to use the pipe but I don't want to fry the engine.

rustycase · Apr 27, 2013

Much of the internal cooling is accomplished by the fuel.
Homelite oil at 32:1 is probably as good as any on the market. I've heard no bad reports on it. Many have oil preferences, but the Homelite oil should suffice...

The pipe may be leaning out your burn, building excess heat.
Try a larger main jet.

And,
36 is a tall sprocket from the stock 44... it will load the engine harder, building more heat.
How much do you weigh?
What is your riding style?

Pls take those factors into consideration.

A chinagirl is what it is...
they are not even up to the quality of a moped.

If you Should be on a motorcycle, a motorized bicycle is never gonna work out for you...

Good luck
rc

borntofli · Apr 27, 2013

China girl is a yugo, moped is a bentley......... But fun and cheap to mess about with.....

Risingsunn · Apr 27, 2013

I weigh about 195, most of the time I try to find the "sweet spot" to run at, with this setup it seems to be around 27-29 mph. When I am testing a new configuration like I am now, I generally warm the engine up then WOT up a slight incline for about 1/2 mile to see where she top off at. Then cruise another 1/2 mile home, and do a plug chop. The plugs look fine, not quite coco brown but not fouled or grey.

But if the motor gets this hot in a 1-2 mile run, it's going to really fry on anything longer regardless of how slow I go.

I don't own a motorcycle I just don't want to get run over when I am sharing the road with cars.

Anyone know what size the stock jet on an NT carb is?

Toadmund · Apr 27, 2013

I believe it's 0.70mm.
My brother had heat issues too with the SBP pipe, his motor got so hot it ran with the spark plug wire pulled!
He had to stop it by dumping the clutch.
Hot Link
He tried to get his motor running this spring again for the first time since this issue, his motor won't start.
Best to try a larger jet that gives you a touch of 4 stroking.

I use an RT carb, my jet is 0.65 and it 4 strokes just a bit until further acceleration, I feel comfortable with that and my motor runs very well.
(No expansion chamber)

Risingsunn · Apr 29, 2013

Time for me to learn to rejet. Hopefully it will do the trick. If not I have have another useful motorized bicycle skill under my belt. Damn, those drill bits are small though.. LOL

On a completely unrelated topic, do any of the vendors here (besides Bikeberry) have a referral program? I have people ask me where I got my motor quite often and don't mind sending them to good vendors, I would like to get a little something for sending business their way!

Toadmund · Apr 29, 2013

Holy crap, referral program indeed, here I am advertising zoombicycles all the time when people start asking questions about my bike, like the guys who showed up where I locked up at the scrap yard.
This happens a lot!

Anyway, Risingsunn, best to start with a jet too big and work your way down (if you have jets to try), unless of course if it's easier to just start small and just drill bigger until a hint of 4 stroking if you have one soldered for the job.

Hope you have a super happy lucky fun time! .wee.

joelogger2 · Apr 29, 2013

thread starter

how do you start a new threa dnut

d

Toadmund · Apr 29, 2013

Go to 'Motorized Bicycle - Engine Kit Forum' below the bikeberry ad, then select where your topic fits from the category menu, then hit the 'new thread' button near the top.

48ccbiker · Apr 29, 2013

my god, have none of you read that the stock ignition timing is way too advanced because they use a 4 stroke CDI? Too advanced means it runs too hot. It isnt rocket science. JNMotors sells a good "2 stroke" CDI with high voltage coil guaranteed to bring the engine temperature down while also getting more power out of it.

Risingsunn · Apr 29, 2013

Sorry 48cc must not have gotten the memo on that. Been combing the forum for months and it musta just skipped my attention! But hey thanks for the insult, I mean the information and the shameless plug!

Toad,
Yeah I already do have a jet ready to drill. I tried enlarge the hole by using cutting a safety pin off sticking it in my drill and opening it up that way. It got the job done, but the bike ran like crap. lol, I opened it too much. So I held the jet over an open flame for about a minute, stuck the solder in and now I have jet ready for drilling. Now I just have to buy the bits. This hobby is getting to be expensive!

And buying another CDI? Don't think so. I am going to work with what I have, wrong timing or not. I am not going to fork over another $75 for yet another upgrade. I wanted a CHEAP motor to PLAY with, not a speed demon that will nickel and dime me to death. I'll save my money and buy a motorcycle for that.

48ccbiker · Apr 29, 2013

I didnt mean any insult. I think you should reconsider your viewpoint. You didnt buy something that is OK or "good enough". You were basically ripped off and now you have to modify it in order to get it to work right, or you will wind up throwing it in the trash after you seize the piston due to over heating. When you get cancer you cant ignore it or deny its existence, you have to do something about it.
Here is my prediction: you will either ruin the top wrist pin bearing or seize the piston due to the standard CDI. Either way you are looking at doing prevention or repair. And when you repair it are you going to buy another standard CDI? Of course not, you will finally of learned your lesson and given in to the fact that these cheap engines need modifications to work right.

Risingsunn · Apr 29, 2013

48cc,
Again, thank you, but no thank you. I am sure that the CDI that you are, dare I say, "advertising" is great but it's not worth it to me. I would just as soon go back to stock exhaust then spend another $75 that I don't have in my budget. Of course I could also listen to other who HAVE run the SBP pipe WITHOUT a Jag CDI and had no issues either. They might, just might, have ideas too that would not cost me $75+ dollars.

So unless you have something else to add besides telling me that my engine is doomed if I continue on the path I am taking and that my salvation can only be found in a that item, please enjoy your day in another thread. Thank you.

48ccbiker · Apr 29, 2013

The reason it runs hotter with the expansion chamber is not because it requires a fatter jet. It is because the pipe is basically causing more compression at top rpm, in addition to the excess compression caused by overly advanced ignition.
If you dont want to spend more money then just go back to the stock pipe and extend your intake for the benefit of a resonance effect that causes more fuel/air to cram into the engine at low rpm. cost is about $3.

Toadmund · Apr 29, 2013

I made a CDI from rohmell's thread, 'roll your own CDI', it has the retard function.
Now I just need to get a decent coil, and a job to pay for it.

But still, I think the jet sizing is the cure, even though 48cc may be partially right, in that proper retarding may make it run cooler, appaently these motors are too advanced, not tecnologically, of course!

Risingsunn · Apr 30, 2013

I ordered the bits set tonight. Found an awesome deal on another post for an inexpensive set with all the sizes needed.

http://www.widgetsupply.com/product/BLU01.html

It's a good place to start.

So from what I am understanding I am going to be working my way up from about a #70 until I start getting some four stroking. But at what range? 1/4 to 1/2, 1/2 to 3/4, 3/4 to WOT?

A couple of the posts (from other sites) that discuss it:

http://www.affordablegokarts.com/Drilling Main Jets.php

http://www.motoredbikes.com/showthread.php?5988-Re-jetting-Your-Carb-As-Easy-As-1-2-3-(-quarkdude-).

I will let you know how it goes.

Toadmund · Apr 30, 2013

3/4 to WOT with an NT carb anyway.

I have my jet (RT carb) so that it 4 strokes under certain loads or conditions, then evens out. Just a hint of 4 stroking, like on occasion it happens.

Maybe you can go with no 4 stroking at all, just as long as you know you are close to the safe zone.

Scott.D.Lang · Apr 30, 2013

I see something that noone has brought up that could help. Header wrap by wraping the header it cause the exhaust to remove the heat faster away from the head ( or in our cases jug ). Ive done this on 500 plus hp na cars and turbo cars and seen the temp drop as much as 40 degrees. I have wrap on my bike but not for that reason ( I just dont want to burn my leg ). I dont honestly know it will work but its a cheap thing you could try.

Toadmund · Apr 30, 2013

How would putting insulation on the pipe cool the cylinder and head? It just seems counter-intuitive to me.
Bare metal loses heat faster than wrapped insulated metal and in this case the cylinder and the head would suck heat from the pipe, acting like a heat sink, instead of the exhaust pipe losing it's own heat and not transfering it IMO.

Scott.D.Lang · Apr 30, 2013

its thermo dynamics with the wrap around the pipe it causes the gases to move a little faster away from the head and in return pulls heat away. Thats the biggest reason that high hp na and turbo cars do it also because of the effect that is created it can give you a little more hp.

I can give you a example from personal exp I have ( once ) wrapped a header on a inline 6 cylinder 1/2 back on the exhaust to about the middle of the car where the exhaust ended the pipe got so hot that I set the carpet inside the car on fire. scared the heck out of me but proved to me that the wrap was doing as I had been told and helping the exhaust remove the heat away from the head and turbo in this case.

but all that said my experience with 2 strokes is still very limited so when it comes to these small motors I could be bad wrong but whether a 2 stroke or 4 stroke all motors in essence are air pumps so basic principals should still be the same.

Heat issues

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