Putting a new engine in - few questions

[ABB]

Hi everyone,
Just made an account here. My buddy and I are looking to drop a new engine in my old go-kart from when I was a kid. The one that was in before was a Tecumseh 3.5hp.

I don't know much about these small motors and what would be a good way to go. Could you guys give me some recommendations as per these details? Thanks

1. Basic one-wheel drive setup
2. Shaft size is 5/8" I believe (if anyone could confirm a 3.5hp Tecumseh is 5/8" that would be nice)
3. I would like to reuse the motor mount/plate that I have on there already
4. I'd also like to reuse the centrifugal clutch from the old setup.

Basically I'm just looking to drop a new motor in. Is it possible to go up in hp without changing shaft size? I'm trying not to spend over $200, too.

I don't know if this stuff is important, but I know the sprocket I have is 12 tooth, and the next biggest one is 26 tooth and then 60 tooth at the wheel.

Thanks in advance guys!

P.S. - I saw one that could possibly fit: Predator 99cc w/ 5/8" horizontal shaft... but I also read that they're a cheap brand? any insight is greatly appreciated

 

[Doc Sprocket]

Welcome to the forum!

As long as you stay below (typically) 8hp, you should be okay with the existing mounts. Chain length may have to be altered, though. Obviously, you can only go so big while still retaining the 5/8" shaft size. The Predator is a cheapie chinese unit. On your budget you'll probably have to haunt your local classifieds for a suitable used good quality engine. On the other hand, that potentially crappy Predator will come with a warranty.

Whatever became of the original engine?

 

[B.M.800]

For under $200, you can get a brand new predator 6.5hp and a 3/4 bore clutch... OR, like Toystory said, browse you local classifieds often...

 

[ABB]

The original engine shouldn't have anything wrong with it. It hasn't been started in nearly 8ish years (wow) but when I get a jug of gas I'm gonna see if she still fires up. No reason it shouldn't.

I would reuse it but I want a little project to work on, so an engine swap seemed like a cool job. And though 3.5hp was fun when I was a kid, I have a feeling it's gonna be one of those situations when you visit somewhere you went as a kid, and say "oh wow this seemed so much bigger when I was 8 yrs old"... That except with the power from the old engine lol.

Maybe I'll see if I can find someone who wants to trade for my engine and some cash. That would be perfect.

Just doing a little reading, it seems most people are using Briggs engines?

For under $200, you can get a brand new predator 6.5hp and a 3/4 bore clutch... OR, like Toystory said, browse you local classifieds often...

If I were to get a new clutch, would I need anything else or just swap out the parts?

 

[Doc Sprocket]

Well, then- skip the idea of getting a similar-sized engine to re-use the clutch.

Upgrading to a 5-8hp engine will add a lot of oomph. As far as the new clutch question goes- It is possible that you'll need a new length of chain, as it is very likely that the new PTO shaft centre will not be in the same place as the old one, in terms of distence from the axle- therefore, the chain will not be the same length.

There is also a minor possibility that the shaft location on a lateral plane (left to right) will no longer align. This may require an alteration of the engine mount holes locations.

With regards to "most people using Briggs"- I would suspect that's not entirely true. I would suspect that people running their kart's original engines are largely using Briggs and Tecumseh. When it comes to engine swaps, I would suspect that clones of the Honda GX series (most notably the 6.5hp GX200) are the most widely used. This may be due to wide availability, low cost, and an abundance of available replacement and upgrade parts. This is largely due to the ability to swap in genuine Honda parts, and Honda-fitting speed goodies.

Bear in mind that you do tend to get what you pay for. While many people have had good luck with clones (I have not yet begun using mine), the overall quality is not going to compare with the genuine Honda, or indeed Briggs or Tec. I can tell you that my Genuine Honda GX was indestructible. On the other hand, most places have really liberal warranty policies with the clones, and a 6.5hp can regularly be had new for under $100.

 

[ABB]

Well, then- skip the idea of getting a similar-sized engine to re-use the clutch.

Upgrading to a 5-8hp engine will add a lot of oomph. As far as the new clutch question goes- It is possible that you'll need a new length of chain, as it is very likely that the new PTO shaft centre will not be in the same place as the old one, in terms of distence from the axle- therefore, the chain will not be the same length.

There is also a minor possibility that the shaft location on a lateral plane (left to right) will no longer align. This may require an alteration of the engine mount holes locations.

With regards to "most people using Briggs"- I would suspect that's not entirely true. I would suspect that people running their kart's original engines are largely using Briggs and Tecumseh. When it comes to engine swaps, I would suspect that clones of the Honda GX series (most notably the 6.5hp GX200) are the most widely used. This may be due to wide availability, low cost, and an abundance of available replacement and upgrade parts. This is largely due to the ability to swap in genuine Honda parts, and Honda-fitting speed goodies.

Bear in mind that you do tend to get what you pay for. While many people have had good luck with clones (I have not yet begun using mine), the overall quality is not going to compare with the genuine Honda, or indeed Briggs or Tec. I can tell you that my Genuine Honda GX was indestructible. On the other hand, most places have really liberal warranty policies with the clones, and a 6.5hp can regularly be had new for under $100.

Where could I get a Honda GX200 clone this cheap? I googled it and most are $300+.

And if I were to go with an engine that's got a larger shaft size, where would I be able to get a new clutch setup/longer chains?

Sorry if this stuff is simple knowledge I've never tinkered with teeny engines like this... I stick to my LS2 hahaha

 

[B.M.800]

"oh wow this seemed so much bigger when I was 8 yrs old"

My friend has a 3 horse briggs kart, hauls my lead butt all around. Im something like 210lbs 5,11...

Here is a list of places to get gokart parts.
http//www.diygokarts.com/vb/showthread.php?t=1180

I ordered a clutch from MFG supply, I was please with it, got it within a few days after ordering.

 

[oldbikerarlo]

I just bought a 212cc Predator from Harbour Freight, it is basicly a gx200 clone with a slightly larger bore and stroke. It was $100 on sale. That with a clutch and chain, would be well under $200.

 

[r_chez_08]

Where could I get a Honda GX200 clone this cheap? I googled it and most are $300+.

And if I were to go with an engine that's got a larger shaft size, where would I be able to get a new clutch setup/longer chains?

Sorry if this stuff is simple knowledge I've never tinkered with teeny engines like this... I stick to my LS2 hahaha

You can get a real 'clone' here, or you can get a hf predator from harbour freight, which have a different cc, and are harder to mod/ find parts for.

You can get a clutch and chain here. Make sure you get the same chain as you already have. You may also want to change the gearing for your new engine, because it has more power. I personally would buy a new chain if you re gear with a new rear sprocket, otherwise the old chain will wear your new sprockets.

What is the diameter of your tyres, and how many teeth have all your sprockets got?

 

[oldbikerarlo]

You can get a real 'clone' here, or you can get a hf predator from harbour freight, which have a different cc, and are harder to mod/ find parts for.

The only differance, is the bore, stroke, and the gear on the cam is plastic, but will interchange. The carb is the same, all the govenor linkage is the same, the throttle hook up is better, as there are clamps and connectors, allready on it that allow hook up from two differant directions. The only thing I found weak is the air cleaner. It also has more power than the grayhound, I been running the beans out of my Predator for a week now at least 50 miles, on it, still starts first pull and runs great.

 

[ABB]

A buddy of mine were talking about this little project today. What I have now is the one-wheel drive setup right next to the engine. Is there a way to make the axle rotate both tires in the rear rather than just the one?

Also, if I go with the predator 212cc, will any 3/4" clutch work? I chose this one: http://www.bmikarts.com/item/Clutch---35-3-4-400935-3162

because I believe the sprocket on my old clutch was 12 tooth as well (also, it wasn't connected to the other part, cause now I have a loose 12 tooth sprocket in the garage). And call me crazy, but I can't find a clutch from the old setup. Is it possible that it's connected to the rim that is the one used to drive?

The other two gears (or sprockets?) are 26 tooth and 60 tooth at the wheel.

Thanks for all the help guys I really appreciate it

 

[r_chez_08]

You can get a real 'clone' here, or you can get a hf predator from harbour freight, which have a different cc, and are harder to mod/ find parts for.

The only differance, is the bore, stroke, and the gear on the cam is plastic, but will interchange. The carb is the same, all the govenor linkage is the same, the throttle hook up is better, as there are clamps and connectors, allready on it that allow hook up from two differant directions. The only thing I found weak is the air cleaner. It also has more power than the grayhound, I been running the beans out of my Predator for a week now at least 50 miles, on it, still starts first pull and runs great.

Fair enough, I personally would take an exact clone because if I was to ever need new piston rings etc I could find parts.
Its up to you. I like my red clone cos it looks honda

 

[r_chez_08]

A buddy of mine were talking about this little project today. What I have now is the one-wheel drive setup right next to the engine. Is there a way to make the axle rotate both tires in the rear rather than just the one?

Also, if I go with the predator 212cc, will any 3/4" clutch work? I chose this one: http://www.bmikarts.com/item/Clutch---35-3-4-400935-3162

because I believe the sprocket on my old clutch was 12 tooth as well (also, it wasn't connected to the other part, cause now I have a loose 12 tooth sprocket in the garage). And call me crazy, but I can't find a clutch from the old setup. Is it possible that it's connected to the rim that is the one used to drive?

The other two gears (or sprockets?) are 26 tooth and 60 tooth at the wheel.

Thanks for all the help guys I really appreciate it

Yeah that clutch is good. Any clutch with a 3/4" shaft and engagement of 1800-2500 should work ok. Double check that you are using #35 chain by measuring between pins. for #35 it is 3/8" pin to pin, and #40 or 41 it is 4/8" or 1/2" pin to pin.

As far as the sprockets go, that will give you a gear ratio of approx 1:10.8. If you have very large wheels or small wheels and want a lot of torque and low speed that will be fine. If you have smaller wheels I would do away with the jackshaft and just have 12t- 60t, which gives you a 1:5 ratio and with 14" tyres about 30mph. Use this. Enter RPM as 3600. Enter your tyre diameter and gear ratio. For on road you could expect up to about 35mph from that engine and clutch setup. For grass I would say 30mph and hilly fields/ offroad I would say 25mph.

If you got a comet tav2 setup ($200, replaces a cent clutch) I would say on road 40, grass 35 off road 30 or something like that.

Hope that makes sense

 

[ABB]

Yeah that clutch is good. Any clutch with a 3/4" shaft and engagement of 1800-2500 should work ok. Double check that you are using #35 chain by measuring between pins. for #35 it is 3/8" pin to pin, and #40 or 41 it is 4/8" or 1/2" pin to pin.

As far as the sprockets go, that will give you a gear ratio of approx 1:10.8. If you have very large wheels or small wheels and want a lot of torque and low speed that will be fine. If you have smaller wheels I would do away with the jackshaft and just have 12t- 60t, which gives you a 1:5 ratio and with 14" tyres about 30mph. Use this. Enter RPM as 3600. Enter your tyre diameter and gear ratio. For on road you could expect up to about 35mph from that engine and clutch setup. For grass I would say 30mph and hilly fields/ offroad I would say 25mph.

If you got a comet tav2 setup ($200, replaces a cent clutch) I would say on road 40, grass 35 off road 30 or something like that.

Hope that makes sense

Do you mean the wheel/rim? Or the tire itself?

 

[r_chez_08]

Actual diameter of the tire, from ground to the top. Measure with a ruler or tape, cos the tyre can vary from what is written on it.

 

[ABB]

Ok. I think I'm getting new tires in the rear anyways. Is it okay to have taller tires in the rear than in the front?

 

[DaiSan76]

A buddy of mine were talking about this little project today. What I have now is the one-wheel drive setup right next to the engine. Is there a way to make the axle rotate both tires in the rear rather than just the one?

Also, if I go with the predator 212cc, will any 3/4" clutch work? I chose this one: http://www.bmikarts.com/item/Clutch---35-3-4-400935-3162

You can chop off that one wheel drive mess and put in a solid axle, I just finished doing that myself. There are some pics in my build thread. I also used the predator engine, and it works excellent. However, my gearing is too high, so it's parked till my parts come in.

 

[r_chez_08]

Ok. I think I'm getting new tires in the rear anyways. Is it okay to have taller tires in the rear than in the front?

Yep, i have 19" rear and 14" fronts

You can buy live axle parts from bmi too.
Very approximate costings as follows:
Axle $25
bearings $15
sprocket carrier $15
axle hubs x2 $30.
You may need these parts too:
New wheels $30-100
Disc brake $40
Sprocket $15.

Pics would really help.

Another option would be to have a jackshaft powering both rear wheels .

 

[ABB]

Yep, i have 19" rear and 14" fronts

You can buy live axle parts from bmi too.
Very approximate costings as follows:
Axle $25
bearings $15
sprocket carrier $15
axle hubs x2 $30.
You may need these parts too:
New wheels $30-100
Disc brake $40
Sprocket $15.

Pics would really help.

Another option would be to have a jackshaft powering both rear wheels .

I will get pics up ASAP, even though it's torn apart and pretty unorganized as of now.

To convert it to live axle do I need new wheels?

Just thinking right now, here's a question that I feel I shouldn't have to ask hahaha: I have the band brake setup right now from the old setup... how does the cart not drift to one side when braking when the band brake only brakes one wheel?

 

[r_chez_08]

About the brake- that is one thing that has puzzled me too!

You may need new wheels depending on what they are like. You may just be able to get new hubs.