For those with R5 motors with chambers and a y boot.... jetting and carb setup

[m in sc]

I know there aren't many of us, but where did your jet tube & main jet land?  trying to see what a consensus is.

On mine, I'm at a 169-P0 needle in middle with a 155 main (going to go up to 160-165 i think) w 40 pilot on stock carbs, un-ported R5 jugs and pipelyne chambers with a CDI.

was wondering if anyone has had to run into the 169-p2 or 169-p4 area. (stock was an 0-2 or 0-4 for an r5c.)

[gargantua350]

If I remember when I used to have an R5...The jetting I ran was 160 mains with the needle on the 4th position and pilot jet at 50. This was with motocarrera sport chambers and UNI filters.  I ran premix though.  I think the 50 pilot jet was a little rich but I never fouled a plug.  The thing I liked about the R5 was that I never had the mid-range flat spot with chambers. 

[AAAltered]

My similar R5 is running pretty darn good on 155's, 35 pilots, P-0 needle.  I put in all new brass last year.

Stock ports, Y boot, and Millenium chambers at sea level.... Clip in 3 (middle) and a CDI.

[m in sc]

sweet. good info guys. BTW bike sounded great at gap. 

[soonerbillz]

Great thread!
I wonder what a stage 1 ported and bored motor with stock pipes likes for jetting.
Would there be a big difference between what you guys are running?

[m in sc]

Boring has little to no effect in itself, just fyi.

I -suspect- my 70 has had some port work done... i have no idea what as Ive never pulled the top end down and it runs better than it should IMHO. Also has the wiseco 'rattle' and the cyls were stripped of paint at some point before i got it, so somebody has def been in there. I actually run a 16t front sprocket to keep the front end down, it will still power wheelie in 2nd when 'just' warmed up but runs out of power at 8k, probably due to the pipes alone.

that being said, on that bike i run the stock carbs, o-2 jet tube, 145 main, 40 pilot, stock seamed pipes, y boot.   

[RD4140]

Hi hi, bringing back this thread as it's relevant to my current quest. Chasing info on how I should set my carbs up ...

1970 R5 (Engine seems stock)
DG Exhaust
Y-boot w/ K&N Filter
Pre-mix

I'm guessing from the info in this thread a good starting point is -
~150-160 Main
~40-50 Pilot
Clip around middle position ?

Happy to experiment, just looking for a good start.

[m in sc]

my 72 with chambers and a y-boot is on 150 mains, 30 pilots and i think one rich on the needle. as a side note, I actually put mine on a dyno saturday.

dead stock porting heads and carbs, pipelyne chambers, k&n y boot, and above jetting. it put down 36 hp at the rear wheel, whereas they were rated at 36 crank when new, so some gains. and it dropped off dead at 72-7400 rpm. Im also running a cdi with a curve, and the power line was dead straight until it hit peak.

The dyno guy thought i would be embarrassed by it, i didn't care as i expected a max possible of 40, i was quite happy with it. 

[RD4140]

Thanks! I'll start with 150/30 and see how it goes.

[TPR5]

  Agreed 160 / 50

[RD4140]

Tossing up whether to put this in this thread, or in my project thread but I thought I'd park it here as it might help some poor schmuck in the future ....

Whats the go with different dimensioned / style jets? Are these for different series carbs or something? I definitely ordered them for an R5 but I assume there's more than one iteration of the mikuni carbs floating around?

See attachment.

[SoCal250]

For Yamaha R5 & RD carbs (Mikuni VM series round slide) you need the jets shown in your image upper left and lower right.
Upper left = Mikuni 4/042 main jet (also called "large hex")
Lower right = Mikuni VM22/210 pilot jet

There are many types and series of Mikunis that use different jets. One that is easily mixed up is the pilot, as there is another type that looks very similar to the VM22/210 but has fewer holes in the body. The one with fewer holes is not correct for our application, and I believe primarily used for 4-strokes.

[kpke]

Stock RZ350 carbs use the hex main jet upper left in your photo and the small pilot jet lower left. All other round slide Mikunis I have played with use the hex main jet upper left and the larger pilot jet lower right.

[SoCal250]

There are many types and series of Mikunis that use different jets. One that is easily mixed up is the pilot, as there is another type that looks very similar to the VM22/210 but has fewer holes in the body. The one with fewer holes is not correct for our application, and I believe primarily used for 4-strokes.

While looking for something else in my files I came across these that illustrate the difference between the similar appearing Mikuni pilots that are sometimes mistaken for one another. There are actually 3 types that look very similar. The other two types are for CV applications.