Need new engine

[drslyr4]

When the temp is in the 50s it starts good. Below that for get it. The carb has been rebuilt 2 times in the last year from 2 different professional shops. new plugs, air filter, fuel line from the tank. Fuel pump work good. Choke seems to operate properly. I did change the oil in the spring. When it runs it does work but seems sluggish. I gave up trying to get it started. I am going to bring it back home to work on it. Will most likely pull the engine to put something newer.

[mike bar]

Hi guys, its been a while since i've been on here. I had to put my 2 cents in here about the magnum as i have one. They are a great motor but mine does not like warm days as it heats easy. I might try to hook up another fan somehow or an oil cooler so
As far as cold starts I find mine starts best in cold conditions with full choke and throttle wide open until she fires then go right to half choke and fine throttle. Hope this helps and its nice to be back with you guys again.

[drslyr4]

It does restart once i get it running. just a lot of heaaches getting it started. It's just not dependable.

[JohnF]

You ought to add your location to your profile. If you were near me I would come take a look. To me, your complaint here and in the other thread sounds like a carburetor problem. I know you've had it looked at twice already - I've had my carb apart at least a dozen time not including jetting changes. A couple time something plugging some passage and the rest something sticking that darn anti-afterfire solenoid.

Of course if you want to replace the engine - that's a whole different thing. I want to replace mine too with a bigger one like RD did. The 20hp is kind of marginal at 10K ft uphill turn with tracks in deep snow.

But I bet that if you are willing to subject your knuckles to the skinning and the compression checks out that we can fix this.

[North Country Tough]

Spark,compression,fuel,thats it thats all it needs to run,something is missing,I had three magnum 18,s,they all went north sat in 10 to 20 plus below weather and all started fine,if you have good compression then its a easier fix,fuel or spark,find out what the compression is first before wretching the motor.

[reichstall]

not sure on this motor but i do know some equipment i work on if it has any electronic stuff on it may short out when she heats up wont start than it cools down and the circle starts again. these are a terriable promblem to find. almost as bad as we had a guy throw a wrapper from his cig pack in fuel tank it would float around get sucked up against pick kill machine than after i bit fall off and float around again.Not saying this is the deal but i see on my conquest the control box is right there at steering and so it is feasable

[drslyr4]

So an update on this Kolher M18. I cleaned up all of the electrical connectors, ran some sea foam down the throat of the carb. Someone suggested the heads might be full of carbon. It does seem to start better now. I will be doing a compression test next because there seems to be blow by coming out of the dipstick tube. I'm guessing thats not a good sign.

[Frymechanic]

So an update on this Kolher M18. I cleaned up all of the electrical connectors, ran some sea foam down the throat of the carb. Someone suggested the heads might be full of carbon. It does seem to start better now. I will be doing a compression test next because there seems to be blow by coming out of the dipstick tube. I'm guessing thats not a good sign.

Ok, I know you have lots of suggestions to check out but i have a question that may narrow down your search for the problem. When you got the motor back from the shop, did it perform exactly the same each time you got it back? If it did and the compression is good then i would check timing. I know it sounds silly, but attach a timing light if you have one and with the flywheel cover off make sure its firing inside the bracket marks on the flywheel. I'm not 100 percent positive on that engine but there should be an adjustment for the magneto to put it tighter to the flywheel and sometimes a slight timing adjustment. If not then the breaker points should have one. Also clean and inspect the magneto tips to make sure they are free of rust and debris.
If it did perform differently then you might have excessive carbon in the cylinder and valves. I would pull the head and clean the carbon out, clean the valves and install a new head gasket. Hope that helps, and look forward to hearing updates.

[drslyr4]

Did a compression check both cylinders are at 100psi. I was surprized at that. Cleaned the plugs up added some seafoam to the tank, put new new air filter, and changed the oil. Fired right up in the shop and I took it for a spin. Ran real good. I didn't check the timing though, but since its not pinging or misfiring that would most likley mean its on. I think I will leave it outside and see if the problem comes back. I am thinking the heads were carboned up. Thats why I was using seafoam down through the carb. I have used this in the past to clean up interal engine parts and have had good luck. Thanks for everyone help.

[Frymechanic]

Did a compression check both cylinders are at 100psi. I was surprized at that. Cleaned the plugs up added some seafoam to the tank, put new new air filter, and changed the oil. Fired right up in the shop and I took it for a spin. Ran real good. I didn't check the timing though, but since its not pinging or misfiring that would most likley mean its on. I think I will leave it outside and see if the problem comes back. I am thinking the heads were carboned up. Thats why I was using seafoam down through the carb. I have used this in the past to clean up interal engine parts and have had good luck. Thanks for everyone help.

Good, glad its working out for you. Pining or misfiring is not necessarily an indicator of timing being on or not. Still worth a check if its still low on power or if it hasn't been checked in a long time.