DIY/Modded Stubby H-Pipe

[BBS360]

Doesn't look like they've put the MJNs in any CV carbs. I wonder if the diaphragm can handle the different needle setup. The MJN might have more or less drag, or affect the rate at which the diaphragm can move.

Could swap out the stock carbs for a complete Yoshimura set. Probably $500+ to replace both carbs....

 

[16VGTIDave]

Or it could be that CV carbs are not used in performance applications, so they don't make them. A retrofit might be possible, but with the variety of needle profiles, I'd imagine that would be a daunting task.

For $500+, I'd be looking at an EFI conversion like microsquirt, not carbs...

 

[Wolfe_11B]

Yosh carbs are upwards of $1200 last time I checked, and that was for CRs

 

[16VGTIDave]

The only way I'd consider that kind of money for carbs is if I couldn't use EFI. Such as class based racing. And then only if it was the last option to make the power required to win a good prize. Otherwise, I just don't see the value in the cost to performance ratio.

 

[Wolfe_11B]

Yep, that's exactly who uses them. To them, a tenth of a second is worth that much money.

 

[jbristow66]

Made my own set of these on my break at work. 2" through bore with 54mm id/od fittings at each end and a retaining lip to help lock the filter on there. Now i just have to drill and tap for the fittings. Ill post some pics once they're installed on the bobber project.

Tmp_12893-20170317_200231-1942954639

• jbristow66
• Mar 17, 2017
• 2

H pipe replacement for crank case venting

 

[Jeff0133]

Nice work, let us know how they fit...

 

[jbristow66]

These baby's fit like a glove! I had to order my 90 degree elbows since i couldn't find any local, I'm just waiting on them to arrive so i can hook everything up.

 

[jthiessen]

Looks like a good fit. Do you still have the crank case venting into them?

 

[jbristow66]

Yup. Still venting the crank case into them.

 

[jthiessen]

Yup. Still venting the crank case into them.

You happen to have a pic of where they connect?

 

[jbristow66]

I will this weekend, waiting on my 90 degree fittings to come in.

You happen to have a pic of where they connect?

 

[Hawkeye]

Thanks for the info and the documentation. looking at doing this at some point in the future.
I had a wild idea about re using an old hyper charger...for about 2 seconds..bad idea.

 

[xschris]

If you have a sohc xs400 just use a stock H-pipe. They can be had for cheap on ebay.

 

[BBS360]

What's the material? UHMW plastic?

 

[jbristow66]

It's actually Acetal. I had some scrap at work.

 

[mmmboost]

It's actually Acetal. I had some scrap at work.

Acetal aka Delrin.

I think some UHMW would probably work as well and it's much cheaper, plus it's a little softer. It's just a nightmare to turn on a lathe. Stringy/stretchy chips that get caught up in everything including the chuck. I make lift kits for VW Touaregs and I was making them out of UHMW, but I recently switched to Nylatron because it's a much easier plastic to machine, but it is more brittle.

Do you think you're getting a good seal on the carbs with the Acetal? I wouldn't think it would compress that much to make a good seal.

 

[jbristow66]

Acetal aka Delrin.

I think some UHMW would probably work as well and it's much cheaper, plus it's a little softer. It's just a nightmare to turn on a lathe. Stringy/stretchy chips that get caught up in everything including the chuck. I make lift kits for VW Touaregs and I was making them out of UHMW, but I recently switched to Nylatron because it's a much easier plastic to machine, but it is more brittle.

Do you think you're getting a good seal on the carbs with the Acetal? I wouldn't think it would compress that much to make a good seal.

oh yah, I'm sure a lot of other materials would work just fine, this is just what i had readily available for free in 2.5" dia.

You gotta suck those plastic strings/chips off and direct em with an air gun, easiest way to keep them out of the way and off everything.

The fit and seal seems to be pretty damn good, i machined it to be an h7/g6 slip fit. Takes just a little pressure to slide it on, once the clamp is tight you can't budge it.
We'll see when i start it up finally, fingers crossed.

 

[billday]

I'm just embarking on this project for my bike.

I don't have a lathe so I was happy to find this coupler, which fits snugly over the carb but has a metal "shield" to keep it rigid:

https://www.homedepot.com/p/2-in-EPDM-Rubber-Shielded-Coupling-P3001-22/100372290

Now to figure out the rest of the plumbing . . .

 

[BBS360]

Looks cool.
EPDM rubber has a poor chemical resistance to gasoline, though a good resistance to ethanol.
Wont be exposed to gasoline continually but may break down over time.
Give it a soak in gasoline to make sure it'll stand up then inspect occasionally if they do.