500 Two-Stroke Tech

Hi all
After several years, I'm at the final stages of completing my build; just the wiring and carbs to sort out (before disassembly for painting etc)

I'm looking for info on jetting; I have jolly moto pipes and pod filters straight onto the standard carbs. Otherwise standard motor, rebuilt with new pistons and cranks. I've searched a lot through the forum to get a starting point for jetting. Filters straight onto the carbs (Mad beaver etc) is quite controversial on here! The general consensus seems to be that this set up is very difficult to jet and will never work right, especially with standard carbs. But I like the look of it and it was always part of my plan. I'm not too worried about the bike being perfectly jetted so long as it goes reasonably well, I'm prepared to make compromises; I wont be racing this bike!

The best info I have so far was in a post from MC (matt) several years ago, who had a similar set up; "I raised the pilot jet one size larger and did run up to a 380/400 main jet but I think I ended up around 290/300 rears(uppers) & 280 fronts(lowers) I would need to drop the bowls to confirm those sizes thou .."

Can anyone who has run pod filters straight onto standard carbs give me a steer. I want something to get it running so I can get some miles on it before taking it to a dyno. If it feels reasonably good I may forego the dyno. I'm at sea level.

I had the exact same set up except JL pipes. I had brand new Uni filters made. The only note I could find was changing from 250 main to 240. I usually keep very good notes on jetting but apparently haven't on this bike

Subsequently I have swapped out the mad beaver set up for Bill Wilson's K&Ns.

Your mains sound too big for stock(ish) engine. Certainly won't hurt to start big and go down tho.

Good luck.

hi kpke
So you reckon I should be starting at about 250? What about the pilots?
many thanks

Yes. I went smaller from there. Feel free to start bigger if you wish.

Don't forget about elevation. I am at about 700 feet.

Unfortunately I have to use my memory on the pilots. I believe I left them alone. And the needles in the middle position.

I'll bet that I have handwritten notes on this. I never do jetting changes without documenting it, usually on my computer.

I'll try to remember to check my RZ500 note book this evening.

Good luck.

kpke wrote:
Don't forget about elevation. I am at about 700 feet.

I'm at sea level so would need to start on a larger size but not much different for 700 feet??

I looked through my notes and all I could find was a recommendation to use 27.5 or 30 pilots.

When I have a few minutes I will browse through my build thread and see if I have it noted in there.

kpke wrote:I looked through my notes and all I could find was a recommendation to use 27.5 or 30 pilots.

When I have a few minutes I will browse through my build thread and see if I have it noted in there.

Hi kpke
Did you ever get a chance to check your jet sizes?

I'm ready to change the jets now so if you (or anyone) can give me some guidance on sizes that'd be great;
standard engine, jolly moto pipes, pod filters straight onto standard carbs. I'm at sea level in ireland.

many thanks to anyone who can help give me a starting point...

trix wrote:

kpke wrote:I looked through my notes and all I could find was a recommendation to use 27.5 or 30 pilots.

When I have a few minutes I will browse through my build thread and see if I have it noted in there.

Hi kpke
Did you ever get a chance to check your jet sizes?

I'm ready to change the jets now so if you (or anyone) can give me some guidance on sizes that'd be great;
standard engine, jolly moto pipes, pod filters straight onto standard carbs. I'm at sea level in ireland.

many thanks to anyone who can help give me a starting point...

I just checked and could not find any mention of pilot jet size. Sorry. Again, I am pretty sure I left the stock pilot jet in there.