MC49 Tuning help/GK800 steering improvements?

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Adrian Labetti
Posts: 31
Joined: Sun Sep 25, 2022 10:18 pm
Vintage Karting items owned: Mac 49 M/C powered 1960 Go Kart 800
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MC49 Tuning help/GK800 steering improvements?

Post by Adrian Labetti » Wed Mar 29, 2023 9:28 am

Hey guys,
I have a 1960 GK800 with an MC49 m/c on it, and ive been having a bunch of trouble tuning the walbro carb to make any power at all. i've seen many videos online of mc49 class racing, and they have wayy better pickup and rev way higher than i've ever seen with mine (i dont think mines gone past 3.5k). could it be the cheapo walbro sdc/something related to the type of carb? or am i just tuning it wrong? i've been using a 40-1 gas/oil mix, dont know if that helps anything but i'd assume there could be something relating to that. Also, despite tuning the steering to have an outward toe (ackermann), it still has a god awful turning radius, and whenever i turn at low speeds it acts almost as if it was a brake. is there something im doing wrong?
Any and all forms of help/feedback would be greatly appreciated.

Thanks!
-Adrian

Adrian Labetti
Posts: 31
Joined: Sun Sep 25, 2022 10:18 pm
Vintage Karting items owned: Mac 49 M/C powered 1960 Go Kart 800
User Agreement: Yes

Re: MC49 Tuning help/GK800 steering improvements?

Post by Adrian Labetti » Wed Mar 29, 2023 10:04 am

Forgot to add, it’s getting too much air no matter how we tune it. Seems to be the main problem

REAR
Posts: 1221
Joined: Sat Jun 16, 2007 10:19 am

Re: MC49 Tuning help/GK800 steering improvements?

Post by REAR » Thu Mar 30, 2023 5:14 am

Adrian,

Can you explain why you believe it is getting too much air ?

Do not be afraid to open up the adjustment screws on the carb allowing more fuel in. You always want more fuel then not enough. Fuel carries lubrication in a 2 stroke so more the better to a point.

Sometimes a simple spark plug change can also correct problems related to combustion.

R.E.A.R.

Rob Voska
Posts: 1646
Joined: Fri Jun 15, 2007 9:04 am

Re: MC49 Tuning help/GK800 steering improvements?

Post by Rob Voska » Thu Mar 30, 2023 5:30 am

Will it idle down or when started just sit there and rev very fast no matter what?
Go to 6 oz oil minimum and 8 oz is better.

Set toe in 1/16" to-1/8".

Do you weigh 300 lbs? It's only an 80cc engine. Stock carb is pretty small. Stock reed cage is restrictive. Gear ratio? You said it's an MC model. 3/4" crank? If so do you have it geared 12/? You need a 9 t clutch on there with 35 pitch chain.
What do you have for a clutch?

Adrian Labetti
Posts: 31
Joined: Sun Sep 25, 2022 10:18 pm
Vintage Karting items owned: Mac 49 M/C powered 1960 Go Kart 800
User Agreement: Yes

Re: MC49 Tuning help/GK800 steering improvements?

Post by Adrian Labetti » Thu Mar 30, 2023 12:06 pm

When started it typically will try and eventually rev up/run away, although a simple tap of the throttle brings it back down. It has a 12 tooth clutch with a 60 tooth sprocket, and I weigh around 150. The motor has had some gasket related issues in the past, and has an exhaust leak, but I don’t think that’s the main cause. Spark plug is most likely original, so probably a good idea to swap it out, could be the cause.

Adrian Labetti
Posts: 31
Joined: Sun Sep 25, 2022 10:18 pm
Vintage Karting items owned: Mac 49 M/C powered 1960 Go Kart 800
User Agreement: Yes

Re: MC49 Tuning help/GK800 steering improvements?

Post by Adrian Labetti » Thu Mar 30, 2023 12:08 pm

Also, what would you recommend for performance reeds/a different carb? I know they mainly ran tillotsons, what model would fit onto it?

Rob Voska
Posts: 1646
Joined: Fri Jun 15, 2007 9:04 am

Re: MC49 Tuning help/GK800 steering improvements?

Post by Rob Voska » Thu Mar 30, 2023 6:43 pm

You can't fit a 9 tooth drum on a 3/4 crank. You need a tapered crank and a clutch. For starters put as big of a rear sprocket on the axle as possible. That engine does not have enough power to pull that gear ratio. Think more 9/72 instead of 12/60 & it will help a bunch.

REAR
Posts: 1221
Joined: Sat Jun 16, 2007 10:19 am

Re: MC49 Tuning help/GK800 steering improvements?

Post by REAR » Fri Mar 31, 2023 5:33 am

It sounds like you have a multitude of issues so start at the engine first.

How does the engine seem to run with the chain removed ?

Does it rev up cleanly ? Does it rev wildly with the throttle closed ? Will it clean out at upper rpm ?

R.E.A.R.

Adrian Labetti
Posts: 31
Joined: Sun Sep 25, 2022 10:18 pm
Vintage Karting items owned: Mac 49 M/C powered 1960 Go Kart 800
User Agreement: Yes

Re: MC49 Tuning help/GK800 steering improvements?

Post by Adrian Labetti » Mon Apr 03, 2023 10:01 am

Hey all,

Bit of an update, after fixing a leak in the exhaust gasket, it ran quite promisingly, looks like that was a main culprit. would have done more/taken it for a rip up the street, but the $20 amazon clutch i bought for it (i know, learned my lesson with that one) decided it wanted nothing to do with any of it and would grab spontaneously and stall the motor, making a deafening screech in the process (to a point where it just wouldnt allow the motor to start). i've ordered a proper azusa clutch for it, should perform much better/be more reliable. (would have ordered a custom max-torque for it but i didnt feel like dropping $400 on a clutch that would arrive by next year)

Thank you all for the help/feedback, i greatly appreciate it.
I'll update this topic with whatever results from the new clutch/more run time

-Adrian

REAR
Posts: 1221
Joined: Sat Jun 16, 2007 10:19 am

Re: MC49 Tuning help/GK800 steering improvements?

Post by REAR » Mon Apr 03, 2023 7:34 pm

Adrian,

The "deafening screech" sound you were hearing is caused by a dry bushing in the clutch drum. Clutches need to be taken apart periodically and cleaned and the bushing greased with a good high temperature grease. In between cleanings lubricate your chain before each run with a good chain lubricant and make sure that you get some of the chain lubricant in the bushing on the clutch drum.
A dry clutch bushing will actually temporarily seize to the clutch hub and it will not allow the motor to start. Make sure that you do this maintence on your new purchase also or you will experience the same problem you currently have.

If your Azuza clutch does not work for you we would highly recommend calling Max-Torque and ask for the owner, Jim Donovan. Jim is a huge supporter of Historical Karting and he prides himself on servicing karters with a good quality product at a fair price and in a very timely manner. It is safe to say that Jim will be able to set you up with a clutch way below $400.00 in a few weeks at the most.

Hope this helps....R.E.A.R.

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