Mid Range Issues between 5000 - 6500rpm

[CDN_RD350LC]

I wonder if you could shed any light on my mid range issue. My engine really bogs down and struggles between 5000-6500rpm. It idles perfectly and is smooth up until @5000rpm. From 6500rpm on and into the powerband, it screams and pulls all the way to 9000rpm. I have rebuilt the carbs. Cleaned behind the brass balls. Jetted it correctly (I have small can Microns and a stock air box). I also added a set of NK Racing reed valve spacers (6mm) Any air mixture recommendations? Any input or advice would be really appreciated.

[tacky1]

Ohhhhh. The small can microns might be the problem. Notoriously well known for that exact problem.
I have a set on an LC and have much the same problem.
You could play with the needles and see if it helps. Maybe raise a notch and go from there.

[CDN_RD350LC]

Thanks @tacky1! This was the exact feedback I was looking for (to make sure I'm not completely out to lunch). I will adjust the needle and post a follow up. Cheers!

[silverstrom]

Paul...I have a set of small can micron pipes here that I was planning to use on an 88 RZ350 motor. Should I expect similar issues as the LC experienced?

[tacky1]

I think it was the LC that had the problems John. The pv didn’t seem to have the problem. Probably due to the pv having the pvs and better porting.

[silverstrom]

I think it was the LC that had the problems John. The pv didn’t seem to have the problem. Probably due to the pv having the pvs and better porting.

Thanks Paul. That's good news.

[CDN_RD350LC]

Update, I lifted the needles by one slot as per Tacky1's recommendation. It made it slightly worse. I've done additional reading on the RD Crazy forum and per Tacky1's post this is a problem for small can Microns on RD's. Some people have done extensive work to try and make them work flawlessly. I am siding on putting back the stock pipes. I'll play with it a bit more and let you guys know what option I decided on. Cheers.

[Bare]

Ohhhhh. The small can microns might be the problem. Notoriously well known for that exact problem.
I have a set on an LC and have much the same problem.

LC's commonly have a flat spot issue Micron pipes are not the cause.
Mine (1ua engine ) Does Not have the /a stumble issue.. Anywhere .
It revs perfectly cleanly to the 9500 limiter setting ... always has.
Look to your setup ?? If it's capably set, the pipes won't create any issues.. Whatsoever.

[Hooligan]

I entirely eliminated the midrange flat spot on my LC (stock pipes w loud inserts) just by installing a set of 6mm reed spacers. However I note the OP has already installed reed spacers.

[tacky1]

I fired an old set of pipes on to my LC and the flat spot was practically gone. It’s deffo a known prob on the LC with microns. I put the microns back on. I’ll just have to live with it