Velocity Stacks With Screens

Stan:
I'll send you a PM or an email.
Lyn

 

We did about 4-6 pulls per setup, about 4 setups. There was no gas analysis, but we made steady progression up the scale. I know part of the second setup gain was the motor freeing up.

My initial intent for the filters was the sand issue I mentioned, and to "not hurt" power....I was pleasently surprised by the numbers, nothing super-duper, but compared to stacks alone it was an increase.

Sounds like you had fun at Mid-O, good run sir :up: Man, I saw the pics of that 215 bike that was there, his superman, AND it BURNT to the ground later, real bummer, he did a nice job on that bike.

 

For those that don't know, Keith Hamilton, aka #215, had a barn fire a few days ago. The barn burnt to the ground, along with his race bike, other bikes and a '74 Jeep CJ5. A tough bit of luck for a good guy.

 

Gawd...That bike he built? Oh man...He was riding the wheels off that thing too...Damn...That thing was beautiful...He really did a nice job.

Well? Insurance? Is he gonna build another one? He should...Be good for him and racing...

 

Right-on with the dyno wok, well done. To completely verify your setup, change back to your "bad" settings, and you should see a drop in power. If no changes occur, I err on the side of least ignition advance for max power, and richest jetting, ( for air cooled bikes) The last benefit gained is that now you have a setup for a HOT engine, in a hot dyno room.

Stan

 

THANKS very much STAN.

 

These stone guards may be adaptable to some stacks. I've heard from multiple sources that they actually gain 2-3 HP on a TZ750!! Just heresay maybe but some claim better atomization with the turbulence??

http://www.meadspeed.com/products/yamaha/carburettor-stone-guards

Stones and grit are a real problem on the TZ's all the heads I have look sandblasted in the squish area from passing debris. The domed screen on the inlet is a good idea to get maximum surface area and keep some distance from the carb to allow the air to smoth out. I don't like the idea of a smaller screen farther down the throat?

 

That sandblasted look in the squish area of the TZ is caused by detonation, not ingestion of debris. Usually lean with a shade too much advance, mechanical mice gnaw on the squish band. Probably looks a little similar on the piston crown, particularly on the hot side. TZs use open carbs because the rings and pistons will wear out far sooner than the ingestion of grit will take its toll.
First time I went to Kershaw, I took one look at all that fine white sand and got some big ol' green foam air filters. The ones with a big ol' spring inside so they don't collapse at WFO. Put one on the 34mm Mikuni I ran on my MT125r.
Barely made it back around to the pits. Jerked it off of there, said hell with it and let it rip. Turned out okay.
Never ran filters on my CB350 either. But then, it was on a pretty short maintenance cycle too.

 

Unfortunately I'm familiar with detonation too These are larger sharp edge dents clearly caused by debris passing through, This is supported by the presence of vertical scratches in the cyl and piston.

Could have been from a one time off track excursion but most likely years of tire debris getting thrown up. Three sets of heads show varying degrees of this. Ever notice sand and gravel on top of your crankcase thrown up by the sticky tire?

I'll never again run open carbs, the risks outweigh the benefits. If you have room, an unoiled K&N flows more than an oiled one. Filters dust poorly but will catch sand for sure. Dry foam will let sand migrate through if left unoiled.