1988 Eric Gorr(ed) YZ490

[Cdiner2001]

Just got my cylinder head and carb back from Eric Gorr, the
YZ 490 is now a different bike with much more competetive power, he ported the
head and shaved the carb slide. The only problem is that the bike will not idle
now. I don't think that this is a big problem but want to ask anyone here if
they have had the same experience after this modification from Eric and/or if
anyone knows what to do. Do I have to tinker with the needle position , change
any jets? ....etc.?. Also ( not related to the idling problem), I am using an
NGK B8ES , should I be using a different number NGK plug? i.e. hotter spark?.

Pete

[D&L]

Pete,
I cut off about 1/3 of the spring on the idle adjustment screw in order
to screw it in a bit more and increase the idle speed. I think the
adjustment he did on the slide cutaway made a difference somehow. I'm
running a stock 40mm roundslide Mikuni carb with a 430 main and a 30 pilot
with the needle clip in the top (leanest) position. The air screw is 1-1/2
turns out. I was originally running it three turns out but it cleaned up a
lot on the bottom end after it broke in the new rings. The NGK B8ES is
fine. I'm also running an FMF Fatty pipe and Boyesen reeds. It rips. I
went riding last weekend up on Cow Mountain here in California with a friend
who has a stock WR-500 and mine was *much* nicer to ride and faster. He
intends to send his cylinder in to Eric now. :-o

Doug
Sacramento
'87 YZ490 from Planet Gorr

"Cdiner2001" <cdine...@aol.com> wrote in message
news:20000913202642...@ng-bh1.aol.com...

[racer...@my-deja.com]

I'm curious... on my 88 YZ490 Eric recommended that I go to
a R-2 needle jet, which seems considerably richer than the stock
Q-6. However, he also recommended going to a 420-440 main. My
question is, since the main jet screws into the needle jet, what
effect if any does the main jet have on the needle jet?

Does anyone else think the jump from Q-6 needle jet to R-2 is
a bit large?

I am at stock jetting now and the motor has tons of power, but
stock isn't letting the motor be all it can be so I still need
to go in and do a proper jetting job.

I haven't had any problems with it idling, though. I'm running
FMF Fatty and FMF rad valve reeds... although I have some
Boyesen reeds on order and plan to swap FMF reeds out when I
get them.

Jim
'88 YZgorr90

In article <grXv5.199518$i5.28...@news1.frmt1.sfba.home.com>,

Sent via Deja.com http://www.deja.com/
Before you buy.

[D&L]

Jim,
He recommended the same needle jet for me because he claims that the
midrange is too lean. I e-mailed him about it since mine runs fine in the
middle and doesn't ping and he said then don't worry about it. Mine ran fat
on the top and the very bottom when I first ran it with stock jetting. I'm
running 92 pump gas with Maxima castor at 40:1.
As far as the relationship between the main and jet needle, my best
guess would be that the needle jet size wouldn't affect the main all that
much since the main is the primary fluid flow orifice. Try changing your
jetting out to what I have and then if it pings under load in the middle you
might try the R-2 needle jet.

Doug
Sacramento
'87 YZ490 from Planet Gorr

<racer...@my-deja.com> wrote in message
news:8pr9gu$hdc$1...@nnrp1.deja.com...

>
>
>
> I'm curious... on my 88 YZ490 Eric recommended that I go to
> a R-2 needle jet, which seems considerably richer than the stock
> Q-6. However, he also recommended going to a 420-440 main. My
> question is, since the main jet screws into the needle jet, what
> effect if any does the main jet have on the needle jet?
>
> Does anyone else think the jump from Q-6 needle jet to R-2 is
> a bit large?
>
> I am at stock jetting now and the motor has tons of power, but
> stock isn't letting the motor be all it can be so I still need
> to go in and do a proper jetting job.
>
> I haven't had any problems with it idling, though. I'm running
> FMF Fatty and FMF rad valve reeds... although I have some
> Boyesen reeds on order and plan to swap FMF reeds out when I
> get them.
>
> Jim
> '88 YZgorr90
>
>
> In article <grXv5.199518$i5.28...@news1.frmt1.sfba.home.com>,
> "D&L" <yama...@home.com> wrote: