We finally got around to modding my Doodlebug, look in the mod section for my fathers doodle bug with a Honda GX200 on it. For my bike I went with the Harbor Freight 6.5hp engine and a NOS Comet TAV30 Torq Converter for the "transmission".
I originally purchased a Comet TAV2 unit with the aluminum backing plate, I fit it up and realized that the bracing cast into the back side of the aluminum backing plate was going to interfere with the engine mount up. I could grind out one of the webs to make it fit or find an older TAV30 assembly that had the steel backing plate (I had read that they bolt right up with no mods). I sold the TAV2 (making $50 in the process) and purchased two NOS TAV30 units from ebay.
We have a desert camping trip coming up "See Alvord Meet under upcoming events" and we want to take both mini's so we needed to get going on this project. First we had to lay out and cut the holes to re-align the chain and the sprocket on the TAV30 unit. A note here...although the steel backed TAV30 unit will bolt right up to the engine with no mods the "fingers" that hold the plastic cover on interfere with the engine mount plate and prevent the engine from sliding into place. You can see the notch that we cut to allow the finger to clear.
You will need to lift the engine 1/2" to allow the rear of the torq converter to clear the frame. You will also need to cut off the idler pulley/chain adjuster and the tab that the rear chain guard mounts to, they both will interfere with the converter unit. Here's a shot of the 1/2" thick aluminum plate that we used to make the spacer. The notch for the cover "finger" in this pic is smaller than the picture above, I ended up adding a little length so the engine could slide for chain adjustment.
Here you can see the chain roller/adjuster and upper chain guard mount tab has been removed.
Rear of the TAV30 unit. You can see the engine mounted on the aluminum spacer.
Here's a shot of the cover "finger" and a added engine mount plate brace that we welded in, probably not needed but can't hurt.
The plastic cover on the TAV30 unit will hit the frame and keep it from installing properly. A little trimming on the bottom of the cover lets it fit up nicely.
Cover installed.
I wanted to keep the stock chain guard on the back so we cut it down and welded in a new mount tab that doesn't interfere with the TAV unit.
For mounting the throttle cable onto the Harbor Freight 6.5hp engine we had to get a little creative. We used the barrel assy off the stock 2.8hp unit to attach the wire part of the cable and I bent up a side plate from a piece of 520 chain to hold down the outer cable housing. Works great and no need to purchase an adapter etc.
Closer shot of the 520 chain side plate acting as a cable holder.
I was originally going to attach the throttle return spring to the barrel adapter but the cover for the air cleaner was interfering with that setup. I ended up just notching the throttle lever and attaching the spring to it instead. I also removed the wafer washer on the throttle lever and replaced it with a nylon washer/spacer. Now the throttle lever slides nice and smooth without any slop.
Air box installed again. No clearance issues.
All back together again. Now I just have to dissemble the whole thing and give it a custom paint job this winter. Hmmm...I'm thinking KTM orange!
We have two Doodlebug mini's, one with the Harbor Freight 6.5hp engine and one with a 6.5hp Honda GS200 on it. Right now we have a regular centrifugal clutch on the Honda unit. Now that I can ride them back to back I can say the TAV unit is SOOOOO much better than the centrifugal clutch. It's smooooooth, will out accelerate the centrifugal unit, and has a TON of torque off the start now, enough that it's hard to keep the front end down when you nail it. We are currently installing the second TAV unit on the Honda now. I would highly recommend the TAV unit.
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Subject: Honda DB30 6.5hp Engine/Comet Torq Converter install. OH YEAH! 
8/13/2010, 5:31 pm
