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fuzz

Livin' the rat roddin' lifestyle
Joined
Sep 11, 2007
Messages
1,406
Location
Victoria Virginia
This is a story about my adventures with my new toy, 1982 Yamaha xj750. I thought I'd be fun to build a bobber and play on the local streets. Found this Yamaha on craigslist, cheap and with a title but not running but remember I said cheap. So I dragges it home and commenced to get it fired up to see if it was worth working on. Had to clean up the carbs, they get gummed up when a bike sits around, thanks to low quality gas we pay big prices for. And had to cleanup some electrical connects, mostly gounds. Finally got it to run and didn't hear any loud disturbing clanking but the exhaust was leaking around the headers due to 5 of the 8 studs that hold the headders on were broke off even with the head. So I figured I pull the engine out of the frame in order to get the head off to see if I could extract some broken studs. Didn't work out so next idea is to buy a good head to swap on. Found a head on ebay and got lucky in that is wasn't a piece a junk but in fact might be useable. A leak check proved I should do a valve job first and after pullin it all apart, valves, guides and all those cute little pieces in one of these tiny motors actually looked pretty good. But first thing I had to do was make a spring compressor since my automotive type was too big to get in the small hole that the springs were down in. Made one from a C-clamp. After I got all the valves out I found my valve grinding tool is too big for the little valves so I attached a small piece of hose to the end of the valve, put some fine grinding compound on the valve and used the hose to spin the valve till the surfaces looked good. Putting it back together was more fun since everything is small except my fingers. I used small needle nose pliers to hold the keepers that I greased up so they would stick to valves while I released the C-clamp. Boys this is a lot of fun!![cl
 

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I'm rather fasinated with this bike. I've never seen the inside one of these engines. It's a 750cc inline 4 cylinder double overhead cam with hemi combustion chambers. Supposed to make around 80 hp with a red line of 11,000 rpm. The cams are chain drinven off the crankshaft and the chain comes up thru the middle of the engine. Here's a picture of my finger to compare to the size of thing...[P
The intake valves measure 1.3 in diameter and the exhaust valves are 1.1 inches.
 

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Warning ..this is my first attempt at making and posting a video!!:eek:
Anyway I been workin on the bike and it would start after I put the motor back in the frame. So I pulled it again to adjust the valves, which you don't have to do but who reads the manual anyway. Back in the frame it still won't start so after studing a few websites I figured the current ot the ignition box was low so I bypassed all the stock wiring and asorted relays and other junk thats in the stock wiring and ..here's alink to the video I hope..
http://www.youtube.com/watch?v=m7d0tWsW8io
 
Yep it works.

Those jap bikes are fun. Wiring can be a real pain on those bikes. Doing my Honda chopper over right now. And it only has two cylinders.
 
Yeh..the toggle switch was just a temporary fix. I'm going to rip out all the old wiring and wire from scratch with only bare minimum of wires. This bike is loaded with relays and other trouble spots. Don't know if I can find a hotter ignition set up but the spark is weak and I believe it'll run better with hotter spark.
Rode it around the garage about dozens times so the clutch and 1st & 2nd gear work, lots a fun!!..:D
 
Haven't worked on Yamaha a lot. I know with the Honda the wiring can cause a lot of problem. The connectors seem to go bad.

With new wiring and connectors you may have better spark. If not there should be some hotter coils out there. Going with a bare bones wiring is a good idea.

Looks like its a fun bike. Good luck with it.
 
Ripped out the old wiring and wired it up with fresh wire, fuse box and connectors. Removed turn signals, auxilary light and computerized guages. Still have the tach, one headlight and 32 Ford tail/brake lite [speedway item]
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Chopped off the stock fender, seat and sissy bar.
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Bobbed the front fender too. Can't bring myself to paintin the tank flat black cuz I think the it's purdy like it is!!
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What do ya think?? is it a bobber yet?
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