Reed spacers/Y-boot

[iranana]

Hi guys, great to see the forum back! Now that it's summer down under I've been riding the 400c some more. When I last left it, I was trying to jet out the 'bucking' that happens at ~5k with the throttle closed. I've got that down to a minimum, but there's still a flat spot at ~5k before it rips into the powerband.

It's a bit annoying on the highways - either I have to slog it along at 4k or keep it on the pipe at 6k. Bike has Fukui chambers, Vape ignition, pilot jet might be a bit rich at 37.5, and main is currently at 180. Needle 2nd clip, air screw 1 1/4 turn out.

Been wondering whether it's worth moving a Y-boot with a K&N, and also running reed spacers to try and bring back some of the mid-range. Obviously going back to stock pipes would probably be best for torque, but the pair I have are a bit trashed (hence the chambers). Any pointers? My 250E by comparison is really smooth through the whole range, not flat spots or anything. Cheers

[m in sc]

10mm reed spacer and a crossover tube will help for sure.

[iranana]

Ah yeah, the crossover tube - I see they added it on later 400 models - was it added in an effort to help the mid range, and what effect does it actually have? Cheers!

[RDFL]

Was on the RZ350 here, called RD350LC everywhere else, not on from factory 400's. On my 400 helped with the flat spot.

[Organicjedi]

The Dave f mod (primary needle jet conversion) can help with the flat spot too.

[RDFL]

I forgot I did both at same time, so really can't say which if any did better at it.

[pdxjim]

1980 was first year to have the intake crossover from the factory.

It continued on the LC and RZ in basically the same layout, but the RZ crossover tube was bigger diameter.

TZR 1KT/2MA (and TDR250) have a straight horizontal crossover tube between the intake manifolds.

TZR 1KT engine used on the R1Z has a plastic "boost bottle" instead of the crossover tube.  Same exact engine, but they went with a tube on one bike and a bottle on the other.  Weird.

Nerd glasses off.

[SUPERTUNE]

Was on the RZ350 here, called RD350LC everywhere else, not on from factory 400's. On my 400 helped with the flat spot.

Yes, Correct for U.S. 400's no crossover tubes. But the Euro RD400's did I think with the late model DX/2R9's had them stock on the 400's.
I have to use the Primary Needle Jet conversion (called Dave F mod) with crossover or my Team Scream/Barlow designed boost bottles with my TSR 6mm reed spacers and Banshee/RZ manifolds to really minimize this issue to almost nothing.
If still on stock reed cages... using the YZ125 oem reeds also will help over the stock stiffer metal reeds.
Here's Nick setup we did to his for this issue.
We used Spec 2 classic pipes and uni filters on a stg 1 build.
Chuck

[iranana]

Chuck, I always love seeing your work, so pristine! The 400E we got over here did indeed have the crossover from factory... So I'll try adding an intake crossover, y-boot with k&n and the 9mm reed spacers from EconomyCycle, and see how it runs afterwards. Hopefully it has the results I'm looking for

[bhh1989]

Can anyone speak to whether the crossover tube or a crossover bottle is better for addressing the flat spot / mid range?

[SUPERTUNE]

The boost bottles I use are dyno developed/tested by Harry Barlow using Tom Turner software. (Harry and I ran RD's for 2 days on BPM's dyno to see what worked the best on our ported engines)

The Banshee boost bottles don't work very well on the aircooled RD engines.
I use My Team Scream / Barlow designed boost bottles on ported engine setups. On stock engines, the stock Banshee crossover tube works fine along with proper jetting changes.
On MY ported engines...I do run shorter blowdown timings to be able to run 93* ethanol pump gas hotrod builds.
This makes the hard midrange rich burble even worse, this is why I run them and are better at making power above the peak and helps the over rev. (really good for the roadracers)

Chuck

[SUPERTUNE]

Chuck, I always love seeing your work, so pristine! The 400E we got over here did indeed have the crossover from factory... So I'll try adding an intake crossover, y-boot with k&n and the 9mm reed spacers from EconomyCycle, and see how it runs afterwards. Hopefully it has the results I'm looking for

You won't get very good results if you don't rejet the carbs for a crossover setup, I do this by going away from the stock BLEED needle jets to the PRIMARY needle jets and the 5DP7 needle with the air jet increased to a 2.0 or no airjet.
When Yamaha used a crossover on the stock RD's they used different needles and needle jet to get them to work.
So just using a crossover on a std bleed setup won't get the results you may want.
Chuck

[SUPERTUNE]

These pics are for those that don't know what we're talking about.

Stock Banshee crossover tube



A aftermarket Banshee aluminum boost bottle that doesn't work very well on the RD engines.



Here's my TRS/Barlow designed thin wall S.S. boost bottle.

[m in sc]

in my experience, on a stock motor the regular crossover does well. a bottle will work too, but seems better suited for a bike with a bit of 'work' to it.

[iranana]

Thanks Chuck, I have all the main jets etc so I'll try rejetting with the stock needle/needle jet first, but if I have no luck there I'll look at making the switch to the Dave F mod