AC cooling

[_Beko_]

Hello
I have a problem if got a MHR light tunned cylinder and all that comes with that (selletra overrange ipd..) and i think i would probably have cooling problems, so my question is if someone knows how to make better cooling. the engine is piaggio/gilera
Tnx
Have a nice day

 

[tiba_karotsu]

just jet the carb a bit richer so you won't seize the piston but it isn't a solution, a tuned AC cilinder has limits when it comes to cooling. run bigger squish to lower compression.

 

[_Beko_]

But wont that effect on the power?

 

[pr0ve]

But wont that effect on the power?

yes it does but you have to choose...

 

[_Beko_]

what if i live the squish alone, how many kilometres would i make in one without stoping before it was to hot? would it be around 20?

 

[tiba_karotsu]

well it depends on how you ride the scooter, if you tune for power you sacrifice a bit of reliablity, i race aircooled bikes in endurance races so i know a thing or two on what you should do to prevent an AC engine from seizure or detonation resulting from overheating.

since AC engines run hotter you should only use high octane pump gas especially for performance applications, you should also jet the carb one size richer from the ideal jetting the extra fuel will help cool the cilinder. use the best synthetic oil you can buy (the one you can use with the oil pump) Repsol 2T Competicion is a 2T racing oil, it's viscosity is thin enough to be used with an oil pump bes ure to clean the oil tank, oil pump & oil lines, a clogged oil pump can kill an engine in a jiffy. Motul Scooter Power 2T is also an excellent choice i have used it successfully on my 2stroke endurance bike using the oil pump & i didn't have to add oil to the fuel.

use a colder plug like a 9 or 10 for performance applications you don't want to melt the ground electrode while running at high speeds do you. adjust squish clearance to change compression ratio to suit the fuel that you will use, if it still detonates on high octane pump gas then lower the compression ratio till detonation is eliminated.

 

[_Beko_]

i have 28 OKO carb (i went for so big because off coling) and i dont have oil pump anymore, so which oil should i use for premix? sorry if i am anoing but i want to my scooter goes for some while and if you can tell me which from denso spark plug should i use 31. 34...
tnx for answers

 

[tiba_karotsu]

since you're running premix i suggest Motul Kart Racing oil this is the good stuff, most kart engines are AC so this oil should be great for your set-up & i use this stuff too.

for sparkplug IW31 should be fine if you can jet the carb properly.

on our 120cc 2stroke AC endurance bike we run stock carb (22mm) & it doesn't have problems with cooling it has more to do with the jetting than carb size.

 

[Browni]

Hello
I have a problem if got a MHR light tunned cylinder and all that comes with that (selletra overrange ipd..) and i think i would probably have cooling problems, so my question is if someone knows how to make better cooling. the engine is piaggio/gilera
Tnx
Have a nice day

I used AC 70cc race cylinderfor many yeras ago, but for a long time without problem, sure when it becomes too hot you loose performances.

A little bit over-reaching is good, use 0,6-0,7 mm squish and about 10,5 heat range sparkplug or min 31 Denso (31 in denso is equal with NGK 10). You can use an air inlet for your cooling fun it helps a little bit! For my aircool bike I have good experiences with Repsol Competition oil, but a Castrol K-997 is the best in my opinion.

 

[roost]

A big carb won't cool down the cylinder, in reality it's the other way around. Keep the carb properly jetted, since is the fuel evaporation in the combustion chamber that makes the biggest part of the cooling of an engine. Also keep the cooling fins clean.
You may also switch to a fuel blend with ethanol or isopropanol (or run straight alcohol, this will very effectively help to keep the temps in control.

 

[_Beko_]

tnx for all answers you have been a great help