Hello everyone, This past year I have rebuilt my 1974 rd350 in to a cafe racer. I hand made an oil tank tail section and seat. I Installed USD forks from a Honda grom, made some rear sets. I add a speedo/tach into the stock headlamp bucket. The engine was torn down and transmission inspected. I removed all the casting bosses from the cases and smoothed it out. I also tore the crank apart cleaned the flywheels installed new long brand rods with all new bearing and trued the crank. It has a powerdynamo ignition system. The bike was selected for Old bike barn's Greasy Dozen builders collective which happens on memorial weekend in Columbus,OH. I was short on time and money so I had cleaned the stock pistons and cylinders. I had measured the bores with a cheap electronic bore gage and all seemed well so I installed new rings and put it back together. I got It started 2 hrs before we loaded it up to make the 1400 mile trip from Colorado. It would start and idle, you could ride it around the block but it wouldn't make any real power. It wouldn't get into pipe. I tried different pilots and mains but after a compression test I had 91 psi on left and 93 psi on right. I decided to pull the top end off and have it actually measured. We found the cylinders were egg shaped. Which wasn't really a big surprise the motor has 18.5k miles on the stock pistons. So I had cylinders bored and honed and a new set of pro-x pistons. I fired the motor to day and it would rev up from idle easier now than before but still doesn't make power. I was hoping that someone could give me an idea of where I should start with jet sizes. My current set up is this. Powerdynamo ignition set at 2mm before TDC, Y boot with K&N, I did the Dave F carb mod the kit economy cycle sells (drilled the air jet, installed new needle jet, new needle with clip in middle, 30 pilots, 200 mains) new Yamaha banshee manifolds (crossovers capped for now) Vforce 3 carbon fiber reeds (kz85 I think?) JL Chambers (street/race). I live in Colorado elevation here is 5000 ft. The bike didn't run when I bought it, and now i have changed everything and don't know where to start with jetting.
I haven't figured out how to resize my pictures to post. The build of the bike can be seen on Instagram @jake_shellito
What is it doing when it runs, how does it sound? What are you basing your assessment on when you say it doesn't make any power. You could have many things wrong. Are the slides facing the right way? Cut outs should be facing the rear of the bike.
Quote from: JakeS on September 15, 2019, 11:18:00 PM...I haven't figured out how to resize my pictures to post....
Check your PM.
You can let the clutch out and get moving but you can open throttle wide open and no acceleration. I know they can have some hesitation or lag but you can hold it open and it doesn't rev any higher.
Quote from: JakeS on September 15, 2019, 11:58:06 PM
You can let the clutch out and get moving but you can open throttle wide open and no acceleration. I know they can have some hesitation or lag but you can hold it open and it doesn't rev any higher.
Check your slides. They can get switched left for right very easily. If they are facing wrong it messes up the air flow and makes it run way rich. If you do have them wrong just switch them.
I just went out and pulled the slides and it's cut is facing rearward.
What do the plugs look like? Wet, dry, white, tan, black?
8)
Tidy looking bike
The plugs looked wet. No real color on them.
I pulled a set of carbs form my buddies rd350.
They have:
27.5 pilots
190 Mains
514 needles
3rd needle clip
1 1/4 turns out
Installed new plugs. It sounded a little crisper. At 3/4 throttle while riding to would break up. It would not get into the pipe. I was hoping for more answers with swapping carbs.
I read on this forum something about cutting ~2mm off the scoop of the needle jet for the Dave F carb mod. I read through the instruction again and didn't find anything about cutting it down.
Have you seen this posting?
http://www.2strokeworld.net/forum/index.php?topic=54.0
The chart on the last post might be helpful.
I actually had just found that link.
What is you compression now? has to be over 100 PSI to run OK.
Have you verified your timing 2.0-1.8mm BTDC the 1.8 I would use.
Fuel; use good no ethanol fuel
Visit Klemms
http://www.klemmvintage.com/ (http://www.klemmvintage.com/)
JT
crossover tube is kinda important with the Dave F mod and pipes... but I'm the last person to ask about this as I get just as confused lol
An update. I went back and checked timing and it was off. It was set at almost top dead center so I reset it at 2mm before. Made a Dial indicator holder out of a spark plug non-fouler, like the one someone posted on here. Correct timing made a huge difference as you can imagine. I ended up with a leak at the right pipe. A bad O-ring so try sourcing one the right size.
As far as the crossover tube. The way I have read is that these carbs were designed with out one and using one can mask some jetting issues. But I really have no experience with this.
Put the crossover on, It will help for your high elevation to lean it out to pull up on the pipe.
Go fatter with the pilot, 30 is too small, drop the needle one and go down to a 190 at least on the main. (primary conversion)
Did you change your gearing? 14/40 at least, or on a stock non-ported engine 14/41 or 42 in the rear.
These pipes are very race bred and are hard to tune. Spec 2's FTW for me.
Chuck
ive used plugs in the crossover to (initially) get the carbs very initially set up, just to verify it idles ok on both carbs, etc. then tune as chuck says with the crossover. I agree, id move to a 32.5 pilot.