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Old 08-24-2009, 11:07 PM
fishblock fishblock is offline
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Default mounting a gx390 engine to yerfdog cart

Need help, I'm slowly loosing it trying to figure out how to mount my new engine to my yerfdog. I got a gx390, and a comet 40 series clutch setup. My problem is trying to figure out a way to adjust the chain slack from the jackshaft to axle. I'm thinking of a chain tensioner but i have know idea how to build one.
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Old 08-25-2009, 06:19 AM
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take out some links with a chain breaker tool and then add a half link or something if you come up short
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Old 08-25-2009, 07:38 AM
Dsl Lover Dsl Lover is offline
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If you don't need to take out too much slack, you could always raise the engine (Add a steel plate underneath it - Lowes sells 1/4" thick steel plate) - with holes matching your stock mounting bracket.

The only problem with the above solution is that you raise your center of gravity slightly...
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Old 08-25-2009, 10:20 AM
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If your jackshaft is mounted with slotted holes you move it to adjust chain tension you would then move the engine so it's the correct distance from the jackshaft.
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Old 08-25-2009, 07:36 PM
fishblock fishblock is offline
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Here are a couple of pics, I don't have the clutch yet so I'm still mocking up. Although it looks like I may not be able to get the series 40 clutch to fit. Any thoughts?
No engine
Engine
left side - the axle sprocket has to be on this side - no key slot on the other side of the axle. I'm also going to replace brake with a disk setup.
right side
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Old 08-25-2009, 09:40 PM
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jeffm352 had similar space constraints on his kart, I liked the setup he came up with here's his thread http://www.diygokarts.com/vb/showthread.php?t=4915 on your setup I'd try putting the sprocket in the middle of the jackshaft and put a slot in the plate for the chain to go through.
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Old 08-26-2009, 09:53 PM
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You're going to have to move the sprocket inwards a bit, the TC sprocket will be right inline with the beginning of the key way on the engine.
The driven pulley will stick out as much as the OHV cover does.

Also beef up the engine mount... Weld in another support to make 3
I'm running a 11hp clone and I couldn't figure out why I was popping chains all the time on bumps...The bracket broke all but one weld allowing the engine to bounce a lot.
Use 3/16 of thicker for the engine plate too. I welded a 3/16 plate on top of the stock plate.

Also use 420 chain and not 41. 41 will snap easily under the power(i was breaking pressed links a lot until today), 420 will handle the power and torque better.

ALSO! Lol, the best way to mount it is the driven bearing just under the oil fill on the cylinder side, you will need to do some grinding. I'll take some pictures tomorrow and post them after work. This is the only way they fit on yerf dogs and honda engines.

Edit:

Actually here, i had to unplug the charger on my kart. So i snapped some pics.


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Old 08-27-2009, 05:48 AM
fishblock fishblock is offline
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Looks good, I'm starting to lean towards using a tav-2 30 clutch setup. Hows the belt holding up with the 11hp engine? When you said needs some grinding to fit, did you grind the clutch plate, or on the engine?
thanks for the pics, helped me a lot.
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Old 08-27-2009, 02:30 PM
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Looks Good So Far
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Old 08-27-2009, 08:49 PM
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Quote:
Originally Posted by fishblock View Post
Looks good, I'm starting to lean towards using a tav-2 30 clutch setup. Hows the belt holding up with the 11hp engine? When you said needs some grinding to fit, did you grind the clutch plate, or on the engine?
thanks for the pics, helped me a lot.

The clutch plate, there's a "support" fin on the bearing housing that is in the way of it sitting flush, right at the oil filler neck.
The belt is actually holding up fine, I accelerate hard and everything too. I haven't even adjusted the spring. I left it factory.

I forgot to mention, get a 1" sae washer to put between the engine and flat driver clutch plate. it will alight the torque converter, without that washer it will tear up the belt. The spacer they give you is useless since hondas and clones the shaft is like 1 1/8" machined to 1"
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Old 08-29-2009, 05:14 PM
Marvinsanti Marvinsanti is offline
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Wow a GX390 its too much of an engine for a 30 series tc in my opinion... Why dont you consider upgrading to at least a 40 series. They are ususally easier to adjust because they dont use a backplate for the driven jacksjaft. Heres a picture of my dingo with a GX390 and a comet 780 series TC. Bolting everything together was pretty straight forward.



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Old 10-05-2009, 09:10 AM
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I just mounted a GX390 clone to my manco Vortex - similar to Yerf Dog 3206. Anyway, be patient, it took some time and trial and error. You will need to mount both the motor and jackshaft/driven to the same plate. It looks like you have a similar setup. get 2 heavy pieces of angle iron that will support both the engine and new jackshaft assembly. You mount both to the angle iron instead of the tubes. The trick is to get the entire assembly to slide when you adjust the chain. If the tubes are not slottled, then you may have to slot the pieces of angle iron. Use a mounting plate between the angle iron and engine if needed. I spent weeks on this. It was worth it. I just took the thing for its first real offroad trip. Hill climbs and everything - it all worked very well.
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Old 10-05-2009, 09:12 AM
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To repeat someone else's thoughts. I don't think the TAV2 would hold up to a gx390. Maybe in light application. But put some serious load on that & the TAV2 is not going to fare well.
Comet 40 at the least. I used that and it is enought. A comet 50 I hear is better. Depends on what you want to do.
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Old 10-05-2009, 08:26 PM
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Do you think it's possible to mount the 40 series setup on to a tav2 back plate?
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Old 10-06-2009, 04:41 PM
Marvinsanti Marvinsanti is offline
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Quote:
Originally Posted by t0x1k View Post
Do you think it's possible to mount the 40 series setup on to a tav2 back plate?
It is possible, only that you'll need to enlarge the center hole of the backplate where the engine shaft goes through and make it sloted or oval shaped and also drill new holes the bolts that will hold it to the engine, otherwise your driven will sit to close to the driver and the belt tension will not be enough for the cluth to engage.
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Old 10-13-2009, 07:03 PM
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update today. Got the engine mounted, jack shaft mounted.
called comet and was told to use the reverse yellow spring so I could mount the driven clutch backwards on the jack shaft. Had a heck of a time welding wood to the frame of the cart.... Only question I have now, with the kart on stands, and engine running at an idle, the clutch is pulling the belt and spinning the wheels. Is there some sort of bushing that could be missing that the belt rides on at idle, or is this normal for a 40 series?
Here are a couple of updated pics.....

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Old 10-14-2009, 05:36 AM
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It's normal, because there is no load the belt can grab just a little bit and turn them. My 30 series does it.
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Old 10-14-2009, 04:17 PM
Marvinsanti Marvinsanti is offline
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Now it's looking better, just a sugestion, why don't you try and move the drive axle and jackshaft sprockets to the other side so that it is not all cramped up with the torque converter???
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Old 03-24-2010, 03:52 PM
5trucks 5trucks is offline
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Is it just me or do you have the driven mounted backwards? Spring side should be facing the other direction.

Quote:
Originally Posted by fishblock View Post
update today. Got the engine mounted, jack shaft mounted.
called comet and was told to use the reverse yellow spring so I could mount the driven clutch backwards on the jack shaft. Had a heck of a time welding wood to the frame of the cart.... Only question I have now, with the kart on stands, and engine running at an idle, the clutch is pulling the belt and spinning the wheels. Is there some sort of bushing that could be missing that the belt rides on at idle, or is this normal for a 40 series?
Here are a couple of updated pics.....

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Old 03-24-2010, 06:36 PM
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Is it just me or do you have a 65lb 13hp torque monster engine bolted to a kart using wood?

I'd give it about 12 minutes before one, two or both things happen. The wood cracks and messes up the pillow bearings and throws the chain, or the thin jackshaft bends under the torque of the engine and TC and causes all sorts of ****.

I tried mounting a jackshaft setup on a 16hp clone using 5/8" shaft and a centrifugal clutch. It wasn't sticking out as far as your torque converter driven is and it warped the jackshaft basically on takeoff. I had to run it old school with a 10t clutch to a 60t gear.
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