Manco Vortex (616) rebuild no power

[SharpTJ]

So I purchased this kart a few days ago, with the intentions of refurbishing it, it needed throttle cable, return springs, brake adjustment, and a few other odds and ends. Well, I get all the obvious stuff taken care of and figure it is time to ride it. It starts and runs fine, but is seriously lacking power, only getting up to about 12 mph with a 170 lbs rider.

From speaking to the previous owner (no one would EVER lie to me), he says it should run around 30 mph which jived with what I have read on the internet (again, internet is never wrong).

It has the 6.5 hp Suburu Robin motor and Comet 30 series torque converter. How reliable, how often, do these torque converter's need to be rebuilt? And the belt is extremely loose on both pulleys at idle, is that correct?

<---hoping engine hasn't lost compression.... and if it has, could I just bolt on a bigger honda clone with the same TC?

 

[Doc Sprocket]

The belt should be quite loose at idle.

The CVT may require some maintenance- look for a thread on that topic, stickied in this section. There's also a good possibility that the engine needs some work- perhaps the carb. Have you had a look at the spark plug to see if it's fuelling correctly? Try this-

Warm the engine up to operating temp. Get in, and put your foot to the floor. Keep going at wide open throttle for as long as you can, and kill the engine without taking your foot off. Stop the kart and remove the plug. Pay attention to the center, ceramic insulator close to the tip. Describe the colour or take a pic.

 

[Blazkowiez]

Your belt might be worn, your engine might not be revving to or past 3600, additionally you might have a kink somewhere IE: severe wear issues regarding stuck brakes or you really weigh 400 pounds instead of 170 ...

 

[machinist@large]

....... you really weigh 400 pounds instead of 170 ...

Hey!!!! I resemble that remark!!!!

 

[SharpTJ]

Your belt might be worn, your engine might not be revving to or past 3600, additionally you might have a kink somewhere IE: severe wear issues regarding stuck brakes or you really weigh 400 pounds instead of 170 ...

Belt appears to be new, and the proper part. I did a compression test and am at 90psi. Also, I adjusted the brakes (brakes are another issue I haven't gotten to yet) out as much as I could and now I can get to ~17mph, but it is very sluggish. and takes, about 100 yards to get to that 17 mph.

Spark plug is grayish/white

 

[OzFab]

90psi compression sounds ok. Grayish/white sparkplug sounds like it may be running lean; may be due for a carb clean which should solve all your problems

 

[SharpTJ]

pic added

 

[landuse]

Have you ever been able to go 30mph in the kart? Maybe the previous owner is talking a bunch of.......

Just to exclude the gearing as being an issue, post up the TC sprocket tooth count as well as the axle tooth count. Also give us the diameter of the tyres. You never know, it could be gearing all along...

I would give the TC a good clean though as well

The plug looks perfect to me

 

[SharpTJ]

I have never gotten it to 30 mph, but that seems to jive with what I have seen on the internet..from 28 - 32.

18 x9.50" tires, and 9 tooth and 50 tooth sprockets

online calculators seem to put a top speed at around 35mph

update: cleaned the TC and disconnected brakes for a test run and I am still topping out at about 20 mph on flat ground, but the acceleration feels somewhat better..still not where I think it should be though

 

[OzFab]

Even with a cvt, 5.55:1 gearing & 18" tyres are a bad combination. It's no surprise you're lacking acceleration but, that's another story...

Put the rear of the kart on stands, blocks, suspend it from the roof if you have to, get the back wheels off the ground & open up the throttle; what happens? Operate the throttle from the pedal & the engine; is there a difference? This could be a simple case of cable adjustment...

 

[landuse]

18 with your gear ratio is not ideal.

 

[SharpTJ]

18 with your gear ratio is not ideal.

What should the tire size or sprocket ratio be?

 

[landuse]

What should the tire size or sprocket ratio be?

If you want to keep the tyres, i would replace the 50t with a 72t sprocket. If you want to keep the sprocket, then you should get tyres about 15" or smaller.

 

[SharpTJ]

If you want to keep the tyres, i would replace the 50t with a 72t sprocket. If you want to keep the sprocket, then you should get tyres about 15" or smaller.

I ordered a 13 hp clone and a comet 40... You think the tire size and sprockets would be ok for that?

 

[OzFab]

Maybe, depends what size sprocet is on the new driven...

 

[landuse]

I ordered a 13 hp clone and a comet 40... You think the tire size and sprockets would be ok for that?

I think you should then be fine with the ratio you have. Are you sure all the sprocket pitches will be the same?