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Dave F on a 350 with JL pipes

Started by teazer, February 22, 2019, 11:29:12 AM

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teazer

I know this was covered many times on the old board but since I can't search that, I thought I'd start a new thread.

RD350 with ported OEM cylinders, YZ85 reeds, Banshee cross linked inlets, 6mm spacers, RD400 head gaskets, stock 28mm carbs, JL stainless pipes, Y boot with tall K&N filter, DYNA ignition.

Carbs have been stripped and cleaned and drilled and tapped to take air jets.  I am thinking as a starting point (should be on the safe side)
Main jets:   220
Needle:      5DP7-3
Needle Jet: 169 P-2
Pilot jet:      32.5
Air jet:           2.0

I read Dale Alexander said that he cut the spray bar down to 2mm but I didn't see that mentioned in a copy of the Dave F instructions. I am pretty sure that I saw Chuck Q recommend that in the past and he knows what works.

Any thoughts, comments or recommendations?

Thanks

2strokesforever

When I did this it was between 1.5 and 2mm.

I believe it's 2mm for a 400.

Hopefully supertune can verify
1963 YD3
1968 YG5t
1970 Rupp Scrambler
1972 LS2 100
1973 LT2
1975 RD250 x2
1975 RD 125
1975 DT400
1977 RD400 x2
1977 DT/RD
1978 DT400 x2
1980 Exciter 440
1983 CR60
1983 CR80
1991 TZR250R SP
1992 Vmax 750-4

And 1 4 stroke- 2014 Vmax 1700- tuned by Tim Nash

Jspooner

We are at about the same elevation so you should be pretty close except for the P-2 NJ. So far every 250/350 I've done that mod to I've ended up with P-0 NJs. Even on my 350 with big bodied VM30s and other not so mild mods i use P-0s in those carbs too.
"Just quit brain fucking it and get it done"

teazer

Thanks.  TZ's use O-8 so P-0 makes sense.  I decided to start rich because it's not my bike and a couple of jets are cheaper than rebuilding it again. I'll order  a pair of P-0s.

Interesting that the R5 used O-0 but without reeds I would expect more reversion and more fuel as a result, so with a reed motor, slightly richer needle jet seems logical.

Hawaii-Mike

I have read somewhere P-0 for RD350's and P-2 for RD400's.

SUPERTUNE

T, I use 169-P2's and cut the spray shroud 1.7mm.
210's on the mains will about right.
I always start with 35 pilots on Spec II PIPES.
I'm usually also using my TSR/Barlow boost bottle/Banshee manifolds and yz125 reed petals on the stock cages.
So your on the right track. Don't cut the PO's if you use them.
5DP7--2 or 3 is good on a 2.0 airjet.
Chuck at the races at Bloomingdale, Ga (Roebling Road Raceway) this weekend...  8)
RD machine work, boring, porting, cranks and engine building.


Chuck 'SUPERTUNE' Quenzler III
Team Scream Racing LLC
1920 Sherwood St. STE A
Clearwater, FL. 33765
cqsupertune@tampabay.rr.com

teazer

Much appreciated input.  Thanks everyone. I figure that the more I learn, the more I need to reach out, to add to that learning. Can never have too much information.  I really want to err on the side of rich and safe because in my experience, RDs stick most often at part throttle - especially after they have just been run hard. That's why I am starting with P-2s.  They have 7% more annular area at low to mid throttle which drops to 1% different at WOT.

Good luck at the races Chuck. 

BTW, did I understand that as cut down P-2 spray bar but if I use P-0 leave it full Mikuni height.  That's interesting. Tall spray bar gets relatively richer than a short one as revs rise if I understand what Mikuni has to say on the subject.  P-2 is richer so give it a short spray bar to reduce how much richer it gets as revs rise.  P-0 is slightly leaner so leave it full height to get relatively richer as revs rise.  That makes sense but I had never thought to try such a subtle change to clean up mid range. Thanks for sharing that knowledge.