Exhaust back pressure and overheating

[Toby woodman]

Having ridden and built about 5 bikes, and talked to lots of friends about their bikes, i have a few questions about overheating. correct me if I'm wrong but, are the usual overheating symptoms, loss of power and a rough grinding noise, along with a bad idle. when i run a modified, straight pipe exhaust, which I know isn't good for the engine. the overheating stops and they run a lot clearer and smoother. if i were to jet the carb richer and adjust the needle to counteract the lean mixture caused by the exhaust, would this be a good way to stop the overheating. bear in mind that i am not looking for speed or performance, just reliability as the bike is being used for leisure rides where the noise is not a problem

 

[robe]

Rough grinding noises are to be avoided. You may be doing really bad things to your motor. Make sure to mix your gas correctly, I use 40:1 of a good semi synthetic 2 stroke oil. 25ml to 1 litre. Some say 32:1 at any rate mix your fuel accurately. I have been using a enzymatic fuel additive called Startron which really seems to help on all my gas powered stuff. It is only 10ml per litre. So not too expensive.
Most importantly is to check the colour of your plug, whitish too lean, blackish too rich. Milk chocolate brown is ideal. Also maybe run a cooler plug.
You probably know all this but if you are running good with the modded pipe and your plug looks good call it done.

 

[GW's Motorized]

I'm pretty sure Toby had a 4-stroke

 

[DAMIEN1307]

Having ridden and built about 5 bikes, and talked to lots of friends about their bikes, i have a few questions about overheating. correct me if I'm wrong but, are the usual overheating symptoms, loss of power and a rough grinding noise, along with a bad idle. when i run a modified, straight pipe exhaust, which I know isn't good for the engine. the overheating stops and they run a lot clearer and smoother. if i were to jet the carb richer and adjust the needle to counteract the lean mixture caused by the exhaust, would this be a good way to stop the overheating. bear in mind that i am not looking for speed or performance, just reliability as the bike is being used for leisure rides where the noise is not a problem

I thought you were riding a 4 stroke Toby???...You posted this in the 2 stroke section so there is now some confusion here as to the advice in posts being given.

If it IS a 4 stroker you are talking about, let me know so I can move it to the appropriate "4 Stroke" section of the forum and then the 4 stroke folks will be aware and be able to help...If you are running multiple bikes, you will have to be sure to spell out exactly which bike your talking about to get accurate advice.

 

[Toby woodman]

I thought you were riding a 4 stroke Toby???...You posted this in the 2 stroke section so there is now some confusion here as to the advice in posts being given.

If it IS a 4 stroker you are talking about, let me know so I can move it to the appropriate "4 Stroke" section of the forum and then the 4 stroke folks will be aware and be able to help...If you are running multiple bikes, you will have to be sure to spell out exactly which bike your talking about to get accurate advice.

Sorry, running multiple bikes, I’m talking
about 2 strokes

 

[Lance]

I believe larger droplets of fuel do help with cooling

 

[Lance]

I believe larger droplets of fuel do help with cooling

Carb might be getting too hot and fuel is evaporating

 

[ImpulseRocket]

I believe larger droplets of fuel do help with cooling

Smaller do, for one main reason, time. The finer the fuel mist, the more surface area is exposed to the heat for the same volume of fuel, so the faster the fuel evaporates and absorbs the energy around it from the air. The long term and case/internal cooling comes from the oil in the fuel that has a much higher flash point than the gasoline.

Carb might be getting too hot and fuel is evaporating

Also known as vapor lock. It can happen, but it's somewhat uncommon.

 

[Lance]

Wow