fuel mixture/hot run temp

[gwman]

I have a 1996 or 1997 Suzuki DT 200 which has been a great and reliable engine. This year it seems to be running a bit hot and smokes (blue) at idle. 2 questions:<br />1 - Does high octane gas contribute to an engne running hot? Should I step down the octane to 89?<br /><br />2 - how do i decrease the gas/fuel ratio? Is there a screw/adjustment somewhere?<br /><br />Thanks all..

 

[jim dozier]

Re: fuel mixture/hot run temp

High octane gas isn't making your engine run hot. Your engine will run fine on 87 octane. If the idle mixture needs to be corrected there is an idle mixture adjustment on your carbs. The high speed jets are fixed. But a lean idle isn't causing your engine to overheat either. The blue smoke is oil. Check to see if your engine is actually overheating. You should be able to place your hand on the block between the flywheel and the cylinder heads for 5 seconds without burning yourself. What makes you think its overheating, did the alarm go off? Do you have a good pee stream? Are your plugs oil fouled?

 

[gwman]

Re: fuel mixture/hot run temp

jimd - no to all of your questions - no alarm going off, the plugs are clean, the pee hole is clear and the stream is strong. the exhaust port has a carbon (?) build up around it and the paint has actually begun to blister. thats what made me think of overheating. havent placed my hand on the block (yet).I'm not sure. a mechanic early in the year gave the motor a good working over and praised it, excellent compression, etc. I hate to see it blue-smoke and want to take care of any problem. To adjust the fuel/oil ratio if its geting too much oil and i'm going to make it less lean or more lean - i'm not clear on the terminolgy. thanks again

 

[jim dozier]

Re: fuel mixture/hot run temp

The idle mixture adjustment is for fuel/air ratio only it has no affect on the amount of oil injected which is controlled by your oil injection system pump and is metered according to rpm and throttle position. How do you know you have carbon in the exhaust ports, have you removed the exhaust cover? It is possible if you have a hot spot there or elsewhere you may have a blockage in the cooling system. When was the last time you had the impeller changed? Confirm whether or not the engine is overheating first. General causes of overheating are:<br />1. Impeller worn.<br />2. Thermostat stuck closed.<br />3. Cooling system obstruction.<br /><br />How does the engine run otherwise?

 

[gwman]

Re: fuel mixture/hot run temp

jim - this will be the second season on the same waterpump. the engine runs really nice otherwise. advice i got a while ago told me that the shops love to change the pump every year but its good for 2-3 seasons in general. i know what youre thinking - better spend a few dollars now before its a bucket full of dollars later. I'm pulling it in the next few days to get the pump changed. the carbon I see is on the outside - around the outer edges of the port. does any of this make sense?

 

[gwman]

Re: fuel mixture/hot run temp

jim - this will be the second season on the same waterpump. the engine runs really nice otherwise. advice i got a while ago told me that the shops love to change the pump every year but its good for 2-3 seasons in general. i know what youre thinking - better spend a few dollars now before its a bucket full of dollars later. I'm pulling it in the next few days to get the pump changed. the carbon I see is on the outside - around the outer edges of the port. does any of this make sense?