1985 Marathon power loss

[newman0912]

Hi. I haven't done any updates to the cart, but all of a sudden, maybe a month ago, it seems to have lost a bit of power. The high end engine speed doesn't hit that 'high note' of rpm pitch that it used to have, and there is significant loss of power when climbing a small incline in the road. Funny thing is, it still starts easy, and the engine sounds smooth. No sputtering or coughing. It just lost a bit of power for some reason.

I did change the belt this year, but it sits on the pulleys pretty much the same as the old belt I replaced.

One more thing, it does not smoke at all.

Can you recommend some 'first priority' checks I can do to start the troubleshooting process?

By the way, we only use regular gas that does not have ethanol in it.

Thanks!

[cart around]

Remove the drive belt from the driven clutch. Try to squeeze the plates together with one hand. If they lean towards each other at all, it's time for a new clutch. There should be no movement.

[Dabble Inn]

Is it oil injected or are you mixing? If mixing what oil and ratio? Just curious.....

Good on the regular 85 octane gas

[newman0912]

Thanks for the response. It is still running on the original oil injection tank/pump system. I've thought about removing it and mixing gas and oil but haven't done it yet.

[Dabble Inn]

Did you do as CA suggested above about checking the driven clutch?....

Also, I'd check the operation of the oil pump lever and cable . Make sure both are freely moving with the gas pedal and not broken frayed or hanging up........

I'm not saying this is your problem but remember; when your oil injection system fails you won't know it. The engine will get hot, slow down and seize up

[newman0912]

Dabble Inn, thanks for the response. I won't have access to the cart until the weekend. I did not check the clutch but your other comment concerns me. I always thought that if the oil pump failed, the engine would run much better until it failed. But based on what you said that it will slow down, now I'm really worried. Hopefully if it is the oil pump, I've caught it in time before it seizes. I never knew that. Thanks.

[newman0912]

On the same topic, I'm going to change over to premixing oil and gas this weekend. There's no real reason not to.

I'm sure I can look it up, but is there a recommended oil and mix ratio to use?

Thanks again!

[Dabble Inn]

{Quote} I always thought that if the oil pump failed, the engine would run much better until it failed. {Quote}

No no, If it's not getting any oil it would NOT run much better til it failed.......

Didn't mean to worry you, but what I meant was without oil the engine will first get hot from friction then on it's way to a meltdown it will slow and seize. All in a very short time........

I'm still not convinced that's your problem but anytime is a good time to eliminate it and go to premixing.......

Use 2cycle oil with 85 octane regular gas at 128:1, that's 1oz oil to 1 gallon gas. No more no less, I use a glass kitchen measuring cup for 5oz oil and pump exactly 5 gallon gas in a can. Pour in the oil and swish, flip, shake, roll it around the yard etc, then pour it in the buggy

[newman0912]

Update:
Thanks again for helping with this.

Yesterday, I checked the spark plug. Gap is good, and the electrode color is a nice, tan/brown. No oil, no black, and no white. So can I assume that means the oil pump is working correctly?

I removed the rubber boot from the intake of the carb to eliminate any blockage of intake air. Without the boot on, it runs the same, so that's not it.

I checked the throttle and oil cables, all seem in good condition, the carb cables open the carb all the way.

Tonight I'll take off the belt and check the secondary (driven) clutch. If this has sideways freeplay, what's the next step? Is this a whole clutch replacement or a parts change? Also, please recommend a website to buy the secondary clutch.

Finally, I've read a lot of posts about not changing the original carb to an aftermarket. Is there a rebuild kit I can buy for the original carb that's on the cart? I'm positive it's the original carb, and although I've disassembled and cleaned it a few times due to contamination issue from before I purchased the cart, I suppose it could be time for a rebuild.

Thanks!!!

[newman0912]

Update:
I removed the belt on the secondary clutch (driven clutch) and tried to squeeze the two plates together with my fingers. There is very minimal free play in them which leads me to believe that's not the problem.

This may be nothing, but I did notice that the plastic pads on the driven clutch ramps are not touching the metal slanted ramps. The plastic pads are situated right in the middle of the open air area (hope that makes sense).

Could it be that I need to replace the driven clutch spring?

One more thing we noticed. There's a long, uphill trail that we took, going uphill it went pretty slow with pedal all the way to floor, then all of a sudden it seemed to find the right 'gear' and started revving up and went faster uphill. As if the belt was perhaps too far down into the secondary and them somehow found the right spot.

Any ideas?