Crossover tube?

[rd400canuck]

Wanted to ask you guys if having the intakes joined like an RZ is worth the expense on my RD400c ?

All I can find out is that it smooths things out... but unless it's a guaranteed thing I dont really wan to waste money on it.

TY

[2 Stroke Jamoke]

The crossover or boost bottle upgrade is part of the primary carb conversion (from bleed) and I dont think its neccessary unless you're doing a dave f carb mod or carb upgrade with chambers. What are you running on your bike now? All stock?

[m in sc]

ive run it with stock carbs. is it necessary on a stock bike? not really.

[rd400canuck]

Thanks again for feedback, guys :)

[pdxjim]

Just for conversation's sake, the crossover started with a small tube on the LC in 1980.  Same basic setup but bigger tube on RZ.

Then moved down to a straight horizontal tube between the manifolds on the 1KT TZR/TDR and 3MA TZR.

Because the next gen 3XV TZR was a v-twin, they went to individual boost bottles.

AFAIK, the single big boost bottle crossover was never used on a stock Yamaha twin.

[motodreams]

afaik you are correct....probably because it is entirely unproven to have any positive impact.  The only test I have ever seen are in conjunction with other mods which makes the comparison useless.  The balance across cylinders must have had value as it continued and got larger.

[rodneya]

there are a lot of banshees making huge horsepower on big motors. Some guys run billet intakes with integrated crossover, and others separate intakes. I would say it boils down to personal preference as there does not seem to be any real proof either way that one is actually better than the other.
Im buying parts at the moment to build a 4mil 421cc Serval banshee motor with TM34's and will probably go with separate intakes as recommended by Cody at Farm and Sand Toys.

[2steve]

Started off with a stock RD400. Started opening up the intake by way of airbox mod. A slight mid range throttle opening problem became a big one and I couldn't tune it out until doing the Dave F mod.
K&N in the airbox and cutting the lid around the outside filter edge was about the same as UNI pods.

At that point I bought some cheap used Banshee intakes from eBay and went to a crossover tube. Had to hand cut the rubber ears off the Banshee intakes. That brought idle speed up surprisingly and I had to up the pilot jets and go to P4 emulsion tubes.

Splurged and went to Chuck's Barlow boost bottle after that.

No extra power, but a readiness to come immediately back on power after shifting that's pretty cool.

[SUPERTUNE]

Wanted to ask you guys if having the intakes joined like an RZ is worth the expense on my RD400c ?

All I can find out is that it smooths things out... but unless it's a guaranteed thing I dont really wan to waste money on it.

TY

I am going to suggest NO for your build.
All stock porting, stock pipes, stock airbox, etc.
There would be a slight benefit for you with how Yamaha did the DX euro RD400,  but would require some special carb needles and needle jets that Yamaha made, used for the crossover, and are very hard to find.
In my modified setup with chambers and mods...Definitely.
I even have/sell Barlow designed TSR boost bottles that were dyno tested for the air cooled RD's.
Chuck