1975 Yamaha RD350(LC) Preservation-mod Hellride

teazer

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It's not as bad as an actual TZ, but it won't have a lot of bottom end. That said, jetting and ignition timing can make a huge difference. But it will never be like a big fat 4 stroke. My RZ is basically stock and the power valve allows it to run cleanly at lower revs, and then it wakes up around 6 or 7K.
No need for the clutch on up shifts. just back out of the throttle to unload the gear dogs and slip it into gear.
What jetting is in those carbs? You might want to ask over on 2 strokeworld about jetting TM series for an RD or LC. There's a lot of experience over there.
If your ignition has a tacho output, try a different tacho. I found the trailtech to be really cute, but not much use when thrashing up the street. If you have a CDI ignition, you need an adapter to pickup up the high voltage signal from the CDI to coil and convert it into a suitable wave for a regular tacho.
I see that Spike has a Koso tacho on that TZ, so he may be using a modern programmable ignition.
 

irk miller

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I've got oozing out of the front my base gasket. Seems like really loose oil when hot, but then thickens almost like graphite bearing grease. I am guessing something related to the transfer ports, but I'm not yet sure how or why. My guess is that the blackness and bearing grease nature is from exhaust. Doesn't taste sweet, so can't figure if coolant is contributing. Not in crazy amounts, but enough to know it needs fixed.
 

pidjones

Over 1,000 Posts
I get similar on the header/muffler joints on my RD400. So, odd that it would show up in that area on yours looking like exhaust deposit. Might try a trick that I've been using a lot lately - UV flashlight in a darkened room shows both oil and fuel traces.
 
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teazer

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Needs more high temp RTV around the exhaust flanges. Crude, but two strokes tend to leak black tar like burned oil all over the front of the motor and it usually comes from the header to flange or flange to barrel joint.
 

ex119x

Been Around the Block
Needs more high temp RTV around the exhaust flanges. Crude, but two strokes tend to leak black tar like burned oil all over the front of the motor and it usually comes from the header to flange or flange to barrel joint.
I always called that mung and drool. The only 2 stroke race bike that didn't do it in my experience was the RZ350 that we endurance raced.
 

irk miller

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A pilot jet clogged and a carb started pissing fuel, so I took the opportunity to swap in a 40 pilot and 230 main while I had them apart. Another fun night ripping around the neighborhood.

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irk miller

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The jugs are off to Mototech for bore.
Stretching to 64.5mm RZ pistons with modified skirts.

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irk miller

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I found the tank damage to be a little worse than I thought, which made me adjust the approach to my repair. I had hoped the tank didn’t leak, or maybe lightly seeped, but it wasn’t t cracked. Turns out it was cracked pretty good. So, I dug through the gel coat and got myself down to clean glass and enough depth to apply a layer of .30mm fiberglass mat. Add System 3 silica thickener to the epoxy to build height and paint vertically.

I’ll follow up with a coat of epoxy on the inside of the crack.

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irk miller

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I coated the tank in a GM color called Olympic White. I'm going off a hunch that the white is a common Chevy white and a common Chevy blue. I am predicting the blue is an engine block color. The white seems to match perfectly. Even my wife agrees. #science

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Hurco550

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Really glad you were able to save that tank. It has a neat history, and that damage likely was sustained doing real life privateer racing back in the day. Nice save.
 

teazer

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Great save for sure, but HTF did you get it that smooth? My fiberglass work always ends up with dips and lumps after a lot of sanding.
But the real question is why is that side made of fiberglass? Is that an FRP replica of a stock steel tank or a steel tank with modifications?

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That's my version in the spray booth drying area. Mine is and inch or so less wide at the rear than stock and has a fuel cell underneath it.
 

irk miller

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Great save for sure, but HTF did you get it that smooth? My fiberglass work always ends up with dips and lumps after a lot of sanding.
But the real question is why is that side made of fiberglass? Is that an FRP replica of a stock steel tank or a steel tank with modifications?

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That's my version in the spray booth drying area. Mine is and inch or so less wide at the rear than stock and has a fuel cell underneath it.
Hurco has the story, but it's a replica tank. Weighs hardly a pound. All glass with some aluminum mounting framework at the back. I had to add two tabs to the frame at the back of the tank to mount it. My understanding: the guy who originally raced it made it himself. The craftsmanship is very high.

As for the smoothness of the glass, the trick is to be really tight on depth and sand the repair area really smooth. The gelcoat is typically very even, since it's painted into the mold first. If you evenly cut through the gel coat, the repair area will be perfectly level. I paint a thin layer of epoxy without the silica first to act like glue. Roll out the mat like wallpaper and squeegee with a roller, then add another layer of thickened epoxy with silica on top. If the glass is .30, then my depth is no more than .50. I probably have .30mm of epoxy on top of the mat, so plenty to sand way. That way, the mat doesn't have to be perfect. When I sand, I use rectangles of foam behind the sandpaper. It's cut from that puzzle foam they market for kids playrooms or basement floors.
 

Hurco550

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The tank was made by, or at least commissioned by, the Bishop Brothers out of Mansfield Ohio. Bill and Larry Bishop had either 4 or 5 of them made up for their race bikes back towards the end of their privateer racing days. I think all but two were destroyed during racing, and Bill still has the other one on an RD. Larry has unfortunately passed, but Bill is still kicking around his mc salvage yard. Here's a picture of them back in the day at Daytona Bill standing, Larry on the bike. The second picture is Larry on what is supposed to be one of the first ever TZ700's imported to the states. I've spent many an hour sitting with Bill and Larry at their shop soaking up every story they will tell about racing the old Yamaha 2t's back in the day. As an aside, this bike the tank, the fairing and the seat all came from their salvage yard. Though it's getting pretty picked over, I've seen some real treasures in that place.

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