1975 Yamaha RD350(LC) Preservation-mod Hellride

irk miller

You've been mostly-dead all day.
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I shaved the YZ reed cages to fit the RD intakes. I assume this was the thing to do vs porting the cylinders.

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teazer

Over 10,000 Posts
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That's what I really like about this place. People have different ideas and ways to tackle problems.

Most of us that work on Yamaha twins automatically open up the reed box to squeeze in larger reed cages and never think that maybe there's enough metal in the cage to shave a little off. I would have opened up the reed box and fitted Vito's (or others) reed spacers. If you haven't broken through the sides, go for it. I will have to remember that next time I work on a Yamaha twin.

You should also shave down the step on teh inside which can be done with a file or die grinder or porting tool or a Dremmel.
 

irk miller

You've been mostly-dead all day.
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Fourth front end combo and think I finally found something I like. It’s a CB900 triple with CB650 forks. Gets me 37mm stanchions and an aftermarket for springs and emulators. I’m running the CB900 triple because it’s over an inch narrower
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Hurco550

Keep er' Between the Ditches
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I like it. Also, be careful taking too much of the bondo off that fender. That weight might be needed to keep the front end down... ;)
 

teazer

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Third time is the charm. Upgrade and still looks period appropriate. Good choice.
 

irk miller

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Here’s a little prelude to an idea I’ve been sitting on for years. Converting a Honda CT90 fuel tank into an airbox. To make it work, I’ll have to form the inlet. This may or may not stick. It took four tries on the front end. LOL

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teazer

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That's two attempts so teh winning one must be next. :) RD's hate filkters with flat metal backs. They create a reflection to teh reversion wave and tend to create a rich mixture that can't be tuned out. I would try a Y boot or if that won't fit the flats, try a pair of 15 degree UNI foam filters. They will hopefully angle in to miss the frame tubes.
 

Hurco550

Keep er' Between the Ditches
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I was about to type the same. Though I've not personally dealt with it, I've read many posts on the old 2strokeworld and Facebook forums claiming the same issues. They do look good though, which is unfortunate if they don't perform well.
 

irk miller

You've been mostly-dead all day.
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Hopefully, I’m winning here.

Going for an X-pipe through the frame.

I have rubber elbows on order to replace these scraps. More of a utilitarian approach, but for air I think utilitarian is good.

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teazer

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That's interesting. I actually like the airbox idea you started with. I am told that 2 strokes like a short intake and that's what we run on the RD/TZ drag bike. On the Phat Trakka I tired long UNI filters and bellmouths and short custom intake horn to smooth the intake flow and to be honest I couldn't really tell the difference with the seat of pants dyno.

What I think might work is an airbox of whatever shape and volume makes sense but on oversized stubs to the carbs so that the carbs see a short tuned length but they are drawing from a plenum, if you get what I am on about. Your X pipe may just fit the bill because both draw from the same large volume with twin filters and reduced restriction, but try to make the connection to the carbs (and the X pipes) larger diameter if that's possible.
 

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Brodie

Gold Coast, Queensland
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That looks like a good start.
How well will it flow across the flat section?
 

pidjones

Over 1,000 Posts
Makes me glad I stayed with stock on my RD400c build. Going with different carbs probably negates any need to worry about the original arrangement and gives you a clean sheet to develop your own setup.
 

irk miller

You've been mostly-dead all day.
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Makes me glad I stayed with stock on my RD400c build. Going with different carbs probably negates any need to worry about the original arrangement and gives you a clean sheet to develop your own setup.
Your RD400 probably didn’t start as a pile of random parts like this bike. LOL I think it’s actually more expensive to restore this bike stock vs making the piles of parts I have work together.
 

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