Yerf needs more HP. Which engines fit?

[SilverDuck]

My Yerf has the Tecumseh PowerSport 6HP engine, and it just isn't cutting it. I want to add a larger sprocket on the jackshaft, but the 6HP engine I have now is not enough to turn the 10T sprocket that is on there now. What engines do you recommend for ease of swap? I found a Tecumseh 10HP SnowKing engine for a snow blower, the shaft is exact same as the 6HP PowerSport. Will it be a real nightmare rigging the throttle?

What other engines do most people swap onto these Yerfs?

[joshstep1]

Well, I used a Briggs and Stratton 8.75HP on my old Manco Vortex. That originally came with a 6.5HP Robin and I freakin ran that engine into the ground! The extra 2.25HP really made a difference. I was impressed. If you have a bunch of money to blow, I know Robin makes a 13.5HP engine, and I can imagine that thing is ridiculous. Heres the Robin http://r o b i n a m e r i c a.com/series.aspx?sid=9 and heres the engine I bought http://www.b r i g g s a n d s t r a t t o n.com/engine_power/engine_details.aspx?pid=88

[SilverDuck]

How much welding/cutting is required? I don't have a welder....looking for something I can bolt on and possibly drill a few new holes, if needed.

[joshstep1]

I didn't have to do any modification to the frame to make it work. It bolted right where the old Robin went.

[SilverDuck]

Any issues making the throttle cable match up?

[joshstep1]

I did kinda have to jerry rig that on, but it wasn't too hard.

[SilverDuck]

Do you think one of the Tecumseh SnowKing 10HP engines would work? The crankshaft is the same size as the 6HP PowerSport. The first problem I see is that the pull starter pulls towards the front, not the back. Does that mean the engine rotates the opposite direction?

[SilverDuck]

I think I am going to go this route:

http://cgi.ebay.com/Robin-Subaru-Eng...item45f2a980ec

Robin Subaru 9HP engine, 1" shaft. I will then just need a 1" bore Comet 30 driver clutch, right? From what I've read, these Robin engines are very under rated as far as power and torque. Will this give me a noticeable performance gain over the stock 6HP tecumseh?

[joshstep1]

It SHOULD work. The bolt pattern on the bottom looks the same and they are pretty universal. You'll have to run the kill switch to the steering wheel. Can you get a pic of your buggy up?

[SilverDuck]

What part of the buggy would you like to see?

[joshstep1]

Just a pic of the buggy in general and where the engine mounts.

[SilverDuck]

[kliff]

I don't know wheter your clutch/cvt would fit, or hold up....but HF has 13HP engines on sale again, throw a 20% discount coupon on top of the sale price, and the last 2 I bought were under 300.00, the 6.5's w/coupon, around 107.00

[SilverDuck]

What is HF? Harbor Freight? Would a no-name 13 really have that much more power than a Robin/Subaru 9? I've read that the Robin Subaru's are really under rated.

Have you ever mounted that 13 on a kart? Do they come with a spring loaded throttle?

[EJ Mac]

If I'm not mistaken I believe all the Harbor Freight motors are Honda clones, I could be wrong ,but I know the 6.5 HP ones are and I believe there are mods available for the clones whereas nodda for the robins.

[SilverDuck]

Ok, after some reading, I think I am going to get the Harbor Freight 13HP engine and a 1" bore Comet 30 driver clutch, and use my existing driven pulley.

Problems will include, but not limited to, matching up my throttle cable, and removing the governor.

Since I will be gaining more than twice the power, I want to add taller gearing. Should I go bigger on the jackshaft sprocket, or smaller on the axle? Do they make bolt on sprockets, or will I need to fab a sprocket?

[BuggyMaster]

What you have to watch out on the Yerfs like that is how the adjustment system (both belt and chain) are set up. I can't quite tell from yours, but the way ours was set up, there was a main plate that could move to allow you to adjust the jackshaft location and then the engine could move on top of that plate. The problem it presented (using a fantastic Robyn Suburu engine was we had to extend the slots that the engine mounted to. It was a PITA but it did work. Although the mounting holes are the same bolt pattern, what is different is where the shaft sits in comparison to the factory engine.

Harbor Freight does in fact have some kick ass sales on their clone engines. We have run many of those engines and ran the piss out of them and they held up great. There is a company called SmallEngineWarehouse that runs on ebay and has their own website that were the best place we found to deal with price wise when looking for new go kart engines. The Robyn 7hp engine typically listed for $600 +/- and they had it on ebay for $330 shipped. A super engine.

I will also offer this advice, after we did this, for the amount of money we had in the machine, we could have found a decent mini buggy. We sold he yerf, and bought our first Helix and never looked back. Night and day difference.

Good luck!

[SilverDuck]

I just bought a like-new condition Helix 150 a few weeks ago. I gave my 9 year old son the Helix, and I took over the Yerf. He is much faster than I, so I want to beef up the Yerf so we can be more competitive.

I paid $800 for my Helix, and it was like new. The only problem it had was a broken plastic shifter disk, so it has no reverse. I ordered a new metal disk, and it should arrive any day now.

I'd love to find another Helix near Central PA. There is one for sale locally, but the guy wants $1500 for it. I'm not paying $1500 for a Helix.

If I can put $400 into the Yerf and make it into a monster, I think it would be a worth while project.
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As for my Yerf...the jackshaft is on a plate, and the engine sits on that plate. That plate, with engine, then bolts to the chassis of the kart.

Are you saying that I will need to drill the plate the engine sits on, or will I need to drill the chassis of the kart? Also, could this problem be solved by using a different size belt, rather than drilling the jackshaft plate?
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EDIT: I found the Robin Subaru 9HP for $300 shipped, new. Would that be a better engine than the 13HP Harbor Freight clone engine for the same price?

I have been reading, and some people seem to think the 13HP engine is way overkill for the Yerf, and I might not be able to use it's torque without bending jackshafts, motor mounts, breaking welds, breaking chains, and killing jackshaft bearings.

This in mind, help me chose between the 11HP Harbor($240), the 13HP Harbor($280), and the 9HP Robin/Subaru($300).

[EJ Mac]

Here is a few videos of a Carter Talon in the Philly area for $800 if it has not sold yet. http://www.youtube.com/watch?v=rAEpZNgZXmM
http://www.youtube.com/watch?v=-36Ye7ap11Q

[joshstep1]

I would say the Robin would be a better buy, just because I think Harbor Freight engine are crap and I know Robins will keep going and going and going.

[EJ Mac]

Here is a new craigslist link for the above mentioned Carter Talon it is a 150cc with a koso clutch, supertrapp, and a few other goodies in really good shape. http://philadelphia.craigslist.org/mcy/1733017870.html

[dambull]

So what motor did you end up going with?

[yerftexas]

would like know how it played out i also have a yerf and need more power

[Carp]

SilverDuck.....I used a Subaru EX27 on my daughters kinroad buggy.... It is a huge engine....265cc....huge in size also! My Tav-2 aluminum plate had to be modified (thanks to Buggymaster's info)...VERY POWERFUL. Seems to overpower the Tav-2.

[Carp]

If you are running on hilly terrain and moderate straights, ditch the tav-2 because it wont even shift out of low gear. Run a good 10 tooth cent. clutch (#40 chain) to a 20 tooth jackshaft sprocket then a 10t gear to the axle sprocket.

[Carp]

You can always change the 20t sprocket to less teeth for more speed.