Engine swap.

[Griff726]

Hi guys. First post here. I recently acquired an old concessions kart. Equipped with an old Honda g200. I was told it doesn't run, so I went to work. I have almost 0 knowledge of small engine repair, but I went at it anyway. I replaced the pull cord first, as it was broken. It wouldn't budge afterwards. Using a large screwdriver, I was able to get the flywheel to rotate. It would get stuck at certain points in the cycle. Next I removed the head. I noticed that the intake valve would rise at the correct point in the cycle, but not come back down without pushing it. I thought about rebuilding the Honda, but decided to buy a predator 212 instead.
The original engine had a wet clutch 2:1 gearbox on it. I was in the process of bolting the clutch onto the predator when I realized that the drive shaft on the predator was longer than the g200 and the clutch won't fit properly. The last part of the assembly doesn't slide over the drive shaft, but bolt to the end, so length is critical.
I guess my first question is, can I hack 3/4" off of the predator drive shaft? Should I return the predator, and keep trying to fix the Honda? Or should I get a new clutch for the predator? I'm not a fan of this last option as I already got flack from the wife for buying a new engine.
Sorry for the long post. I'll add some pictures.

Thanks guys!!!

 

[Griff726]

So, I really want to hack 3/4" off of the drive shaft on the predator. Is this a bad idea? Help.

 

[justinlogue5_0]

Don't hack off the end of the crankshaft. You will loose most of, if not all your threads for mounting clutches. It looks like your best bet would be to modify the engine plate ,as in cut and weld a new one in place or just make new hole slots for the predator motor in the existing plate.

 

[Griff726]

Don't hack off the end of the crankshaft. You will loose most of, if not all your threads for mounting clutches. It looks like your best bet would be to modify the engine plate ,as in cut and weld a new one in place or just make new hole slots for the predator motor in the existing plate.

The engine placement isn't the problem. The wet clutch/gear box won't mount to the motor with the shaft that long.

 

[justinlogue5_0]

Hope some one else comes along because I am not familiar with the workings of the wet clutch. Just looking at I have a question. Is there a shaft seal between this clutch and the block itself? If so can you make some spacers and use longer bolts to space the clutch away from the block? Letting everything else align back up?

Again just throwing ideas out there because I haven't messed with one of these set ups.

 

[KartFab]

A crankshaft bolt as a rule of thumb, needs to thread into the crank 2.5x its diameter. Look up the manual and check the length of the crank threads. If you can end up with 2.5x(5/16) of threaded crank after the cut, then I see no justification for keeping it long.

 

[B.M.800]

Did you try to get the Honda running?

 

[Griff726]

A crankshaft bolt as a rule of thumb, needs to thread into the crank 2.5x its diameter. Look up the manual and check the length of the crank threads. If you can end up with 2.5x(5/16) of threaded crank after the cut, then I see no justification for keeping it long.

I'll check the thread depth, as I think this is the best option.

As far as putting a spacer behind the clutch: this would be my second choice. The problem with this plan is that I would then have the drive sprocket too far over. I can't move the driven sprocket because it would hit the brakes. If I move the engine, the mounting bolts would hit one of the frame rails. Maybe I could move the brakes to the other side.

The honda: it could probably be fixed. I just don't know exactly how, and I'm afraid of putting a bunch of money into it and it still not running. I like the idea of a brand new engine, with a little bit more horse.

Thanks for the advice.

Edit: I looked up the thread depth of the drive shaft. It's only 0.67in deep, so by hacking off 3/4 in, I would lose all of it. Would it be reasonable /possible to have a machinist re-drill and tap it?

 

[Twisted]

Don't cut the crank, the honda wet clutch bore is 20 mm and the predators crank is 3/4. The only options I can see is returning the 212 and finding a rh2x gx200 ,making a sleeve and using a spacer, or buying a genuine honda crank(not sure if it fits).

 

[Griff726]

Don't cut the crank, the honda wet clutch bore is 20 mm and the predators crank is 3/4. The only options I can see is returning the 212 and finding a rh2x gx200 ,making a sleeve and using a spacer, or buying a genuine honda crank(not sure if it fits).

The output bore appears to be 20mm, but the shaft coming off of the g200 I believe is 3/4.

 

[Twisted]

Oh, alright just check it with some calipers before you use it. I tried to swap my gx160 with a gx200 and the crank was too small for a 2:1.

 

[OzFab]

Hmm, you have a whole host of issues here, the simplest solution seems to be rebuilding the G200...

If that's not possible, the next simplest solution appears to be to create a spacer for the trans & replace the pulleys with sprockets; the required 1/2" for the chain against the 2" pulleys should leave you plenty of room to play with...

 

[Griff726]

Hmm, you have a whole host of issues here, the simplest solution seems to be rebuilding the G200...

If that's not possible, the next simplest solution appears to be to create a spacer for the trans & replace the pulleys with sprockets; the required 1/2" for the chain against the 2" pulleys should leave you plenty of room to play with...

I like this idea. Thanks! Are there any other benefits of using a chain vs belt or visa versa?

I spoke with a machine shop today that is willing to dock the drive shaft and re-drill and tap the hole. Do most people here think that it's a bad idea?

 

[Rickracer]

If it were me, I think I'd rebuild and modify the GX200,

 

[Griff726]

If it were me, I think I'd rebuild and modify the GX200,

It's unfortunately not a gx200, it's an older g200. Still have the same advice? Also my skills in that area are nearly 0.

 

[anderkart]

I spoke with a machine shop today that is willing to dock the drive shaft and re-drill and tap the hole. Do most people here think that it's a bad idea?

I think that's a good plan, go for it

PS:
Bring them your old engine with the 2:1 gearbox removed, so they can measure/match it's output shaft perfectly.

 

[Rickracer]

...
Bring them your old engine with the 2:1 gearbox removed, so they can measure/match it's output shaft perfectly.

I agree,

 

[Griff726]

I think that's a good plan, go for it

PS:
Bring them your old engine with the 2:1 gearbox removed, so they can measure/match it's output shaft perfectly.

Thanks! I had the same idea.

I'll be sure to let you all know how this works out.

 

[Griff726]

Update: I went to the machine shop today and brought both engines as suggested by @anderkart. He had a pair of calipers (that I don't) and it turns out that @twisted was right. The honda drive shaft is 20mm and the 212 is 3/4in. Ideally at this point, I would like to buy a torque converter, but I really don't have the authorization to spend that much money right now. I might have to keep working on the g200. I might be back asking questions about that once I get deeper into it.
Thanks again. I really should listen to you guys. It would have saved me an hour car ride.

 

[OzFab]

It's not wasted time if you learn something

Personally, I think it would be cool to see the old G200 running again but, worst case scenario, you could use a shim on the predator shaft to bring it up to 20mm; FYI, 3/4"=19.05mm