problems with engine getting hot very quickly

[ianmanning26]

okay so here's the deal I have a 6.5 harbor freight greyhound clone engine that has served me very well over the last few months. I have remove the governor and install it on the lightweight aluminum flywheel with timing advance. I had a home made exhaust on it consisting of a 16 inch long 1 inch diameter pipe with a briggs and stratton sausage muffler on the end. I took it out yesterday and this thing was writing like an absolute dream I mean it was so responsive it was amazing. no vibration no nothing it was absolute butter. that was with the old stock iron flywheel. today I install the honda aluminum flywheel with the timing advance and it seems as if the engine does not have to get up and go that it did before and it's running very choppy and it vibrates a lot. also the engine seems to be getting very very hot very quickly. I took some readings with my infrared thermometer and the block itself was reading right around 120 which actually seems fine even though I only wrote it for about 5 minutes. however the cylinder head and cooling fans on the engine block were reading 200 + like 210 or 220 and my exhaust header pipe was reading 420 degrees! this seems a bit excessive but honestly I don't know if it should be getting this hot because I never really had a reason to check the temperature before today. the only reason I checked it today because I went to pull the spark plug boot off and I burned my hand on the valve cover. right now the engine has been at rest for well over 10 minutes in the valve covers still reading 108 degrees. does this sound about right or is my engine getting too hot. also if it is getting too hot what could be the cause? I cant imagine the flywheel with the 4 degree timing advance would cause this much of a dramatic change in performance at least not in a negative way. the engine is completely stock with governor removal and aluminum flywheel, other than that it's exactly how I came from the store. I am 170 pounds and it's on an old style doodlebug frame. please let me know because I would really like to ride this tomorrow morning but I don't want to ruin it. also if my chain is too tight will it cause my engine to excelerate slower than normal? thanks guys I really appreciate any info you may be able to give me a really need to solve this problem.

 

[rmm727]

I believe the clone go karters run a cylinder head temp of around 400-425. You might not be running as hot as you think. Check your plug. Whats it look like. Could be a jetting issue.

A tight chain would wear out the bushing in your clutch. The slower acceleration could be due to the lighter flywheel not having enough mass to get the load moving. (though that seems contrary to what is normally said):shrug:

 

[MB165]

The problems you describe are indicitive of overadvanced ignition timing. Dont be so worried about the heat, its gonna run hot, especially in this heat wave were having right now.
Im assuming the flywheel has 5 degrees advance built in? If so, you have a total of 9 degrees added advance.
Its better to choose the RPM range you want to run the engine inside first, then calculate and play with the advance to work within that RPM.
try the key or flywheel separatley and see how it works.

 

[ianmanning26]

i think i paniced for no reason about the temp. turns out you are right, they run these things upwards of 400 degrees for 50 laps so mine is not overheating. i do a lot of small outboard engine repair but those engines are water cooled and should never get over 165 or your in trouble. but that doesnt apply to these air cooled clones i guess. as far as the timing is concerned, i have the aluminum with the built in 5 degree advance, no advance key so i should be right at 5 degree advance right? not sure where the 9 degree came from that you are talking about, unless i just didnt clairify what i was using properly. no advance key just the built in advance with the flywheel. as for the lack of acceleration, i think what happended is that when i installed the flywheel i also cleaned the carb, when i put the carb back on i forgot to reset my idle screw so the engine was idling lower than i normally have it set, therefor it felt like it was taking more throttle than usual to take off when in fact it was just that i had to throttle more because the idle was set lower:doah:
i ran it this morning and it was awesome, not sure why i freaked out, its not like i blew the engine or anything. i tend to overreact i suppose. i def think i need to rejet to make up for the header being on there. i went to ace today and looked for the tiny drill bit set but they didnt have one. guess ill be going to hf to look for one tomorrow. thanks for the input guys.

 

[MB165]

Yeah never mind, I thought I read you also had a 4deg key.ut:

 

[65ShelbyClone]

however the cylinder head and cooling fans on the engine block were reading 200 + like 210 or 220 and my exhaust header pipe was reading 420 degrees!

The header itself was 420°? That's downright cold for exhaust. The exhaust gas temp is probably double that at idle and gasoline engines can put it over 1400° under load.

 

[Bdmitsu]

Drive it like you stole it! !! yeah.. you are fine..use these readings against the honda your building.. im sure you prob will see a big difference:thumbsup:

 

[predator bike]

we run a 400-410 head temp on my race clone its what are engine builder told us to do