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Old 02-20-2014, 10:58 AM
ccasey75 ccasey75 is offline
Motorized Bicycle Newbie
Join Date: Nov 2013
Location: Texas
Posts: 2
Default Vintage Miyata Road Bike - First Build

Hello all - I saw one of these bicycle engine kits online and knew that I had to put one together. I had a couple of bikes in the garage, but this 1991 Miyata 914 SE was the only one that could accomodate the engine in the frame.
_photo 0.jpg
I ordered a cheap kit from eBay knowing that it would be ripe with problems and issues to fix (something I actually enjoy). I set up a work station in my garage with a couple of saw horses, and old door, and I built a wooden stand for the bike based on picute that I saw on one of these forums (KCVale I think...):
_photo 1.jpg
You can see that I swapped the drop-bars out for a 5" riser bar, added a dual-pull brake lever, and went from 700cX23 tires to 700cX28 tires (as big as will fit under the brakes). I also had to replace the bottom bracket with a wider setup to clear the engine housing and exhaust. I just can't bring myself to actuall use the rag-joint sprocket attachement to the spokes (since I have other options), so I researched hubs and options and ended up ordering a Grubee HD hub from piston bikes. I really enjoyed building a bicycle wheel from scratch for the first time. I ordered a rim and spokes cut/threaded to length from universal cycles. Here is the wheel I build when it was trued up and test fitted on the frame:
_photo 3.jpg
The dropouts on this frame are 126mm and the HD hub is ~130, but it still fits OK. The hub came with a 48 tooth sprocket (I would have prefered a 44), and I bought a freewheel sprocket for the pedal driven side. I ended up getting thigs initially fitted up with the engine mounting position raised using an offset mount/adapter on the front. My intention was to improve the clearance between the chainstay and the chain, but I still needed a tensioner. I threw together a spring chain tensioner:
_photo 4.jpg
I had real isses with the chain jamming in the drive sprocket cover with this higher engine mounting position. The front offset bracket allowed for too much side-to-side movement of the engine, which resulted in sprocket mis-alighment and chain jamming. I ended up dropping the engine mounting position back down into the frame and dumping the spring tensioner for a standard setup. This fixed the problem and the bike is up and running:
_photo 5.jpg
I am still running ~18:1 ratio of oil in the gas, and I am having quite a bit of oil being carried through the exhaust, so I am gradually cutting it back. I also think I am 4 stroking quite a bit and will have to lean out the fuel a bit. I am at ~3000' above sea level, so maybe that is enought elevation to require some adjustment. I may look at adjusting the main jet size.

I have added a suspension seat post and a spedometer since the last picture. This has been a fun project. I am trying to take it easy during break-in, but I have pushed things up to ~26 mph top speed so far. I may swap to a 44 tooth rear sprocket eventually. Let me know if anyone has thoughts, comments, or suggestions.

Last edited by ccasey75; 02-20-2014 at 11:19 AM.
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