Big jets = fast?

Re: Big jets = fast?

On Apr 21, 3:16 pm, "HellSickle" <jldnospamee...@comcast.spammer,net >
wrote:
> "XR650L Dave" <spamTHIS...@yahoo,com > wrote in message
>
> news:c565388d-9e84-4844-8b7b-40049dba5514@m3g2000hsc.googlegroups,com ...
> On Apr 18, 11:58 pm, David Kelly <n4...@yahoo,com > wrote:
>
> > My XR650L was barely-runs stupid-lean stock, and even that only needed
> > a moderate re-jet with opening up the airbox. Like 52/155 to 55/158
>
> On a ride last Saturday, my 650L was getting almost exactly 50mpg. This was
> on 200 miles, more than half dirt. Despite running great & giving super
> mileage, the exhaust is black, and every time I've had the head off there is
> massive carbon build-up. I'm thinking that my needle jet seat might be
> worn, but can't get a new one (backordered for a year). The only way I can
> combat the carbon is to do the obligatory high-speed highway run
> periodically.
>
> -Jeff-


BTW, I have no idea how you get 50MPG out of it. At elevation no less.
It must be that long pilot jet I have- that and I probably should be
running a 57 and not a 58 pilot- but last I looked, there's no such
thing?

Dave

Re: Big jets = fast?

Hi!

On Fri, 18 Apr 2008 19:00:50 -0700 (PDT), Craig wrote:
> What is it with people jetting bikes stupid rich? If they think bigger
> = faster, why do they stop at stupid rich?

I my opinion, seems to be that this is the consequence of a series of
misunderstandings:

Normally, the first thing "people" do, is mount a racing airfilter, open up
the exhaust, intake, perforate the airbox like an emmentaler (swiss
cheese) and/or mount a $$$ aftermarket titanium/carbon muffler that adds
another so-and-so much horsepower. Because those people need every single
bit of their bike's power delivery since they always operate it at the
utmost maximum all the time, no matter at what noise level. So it's
perfectly clear that also the jetting has to be "opened up", regardless of
what the status quo is/was. "Opening up" is, as they heard from a friend
of a friend and as everybody knows, increasing every jet size and moving
up the needle a number of notches.

Then there is a number of people who are afraid that their bike might run
lean as the result of a rejetting process and fry its piston. So they stay
"on the safe side" and keep it way rich. Others might have jetted it for
15°C and sea level (pretty much stock setup) and don't care when it gets
"a little rich" at 30°C and 1000 metres. Four strokes anyhow seem to be a
bit more forgiving when it comes to wrong jet sizes. Additionally, staying
a tad on the rich side mellows out the power delivery curve a bit - at
least with my Dellorto-driven 1998 KTM 620 SC, the snappyness seemed to go
away when I hung the needle a notch higher.

Also, I see a tendency that people overoil their filters, because "much
helps much", in a way that the oil clogs the pores and starts dripping
from the lower part of the foam after a while. This will also result in a
richer-than-desired mixture without even touching a jet.

There also might have been an airleak as the result of a damaged intake
manifold, an errorneously mounted carb, etc. etc. (add a variety of
twostroke problems here) that was "compensated" with larger jets by
mistake. Then, after some maintenance, the orignal problem was cured
(probably even unknowingly) and the jetting kept as is, because the bike
"ran fine" with it.

Last thing I can think of is a mis-adjusted accelerator pump. Without the
"BK-Mod" (a pump rod actuator stop mechanism), the FCR-MX carb in my Yam
426F would inject for a whooping five seconds (no kidding) after whacking
the throttle which also makes the bike run way rich. After the mod, I was
down to some below one second which helped a lot regarding response and
out-of-berm-handling.

Moral: Jetting is not an easy thing to do and folks that are unsure about
the where and what should probably thoroughly read some information and
consult a friend with some knowledge before digging into their bike's guts.
Writing down the changes is also a mandatory thing to do. Or buy a fuel
injected scoot and rid themselves of permanent rejetting hassle. ;-)

Cheers,
Volker


--
@: I N F O at B A R T H E L D dot N E T
3W: www .bartheld,net

Re: Big jets = fast?

On Sat, 19 Apr 2008 12:34:43 +0200, Volker Bartheld <dr_versaeg@freenet.de>
wrote:

>
>Normally, the first thing "people" do, is mount a racing airfilter, open up
>the exhaust, intake, perforate the airbox like an emmentaler (swiss
>cheese) and/or mount a $$$ aftermarket titanium/carbon muffler that adds
>another so-and-so much horsepower. Because those people need every single
>bit of their bike's power delivery since they always operate it at the
>utmost maximum all the time, no matter at what noise level. So it's
>perfectly clear that also the jetting has to be "opened up", regardless of
>what the status quo is/was. "Opening up" is, as they heard from a friend
>of a friend and as everybody knows, increasing every jet size and moving
>up the needle a number of notches.

http :// www .crocker,com /~mwilliams/Derestricted_path.htm

Nice write up.

M


--
Mike W.
96 XR400
70 CT70
71 KG 100 (Hodaka-powered)
99 KZ1000P (training)
99 KZ1000P (rider)
00 Beta Rev-3

Re: Big jets = fast?

On Apr 19, 8:17 am, Mike W. <outof...@emailbiz,com > wrote:

> http :// www .crocker,com /~mwilliams/Derestricted path.htm

Yabut bragging about my engine being so powerful that it needs REALLY
SMALL JETS just doesn't carry the same weight...

Craig

Re: Big jets = fast?


"Mike W." <outofthe@emailbiz,com > wrote in message
news:47sj04t6dhc0b1cro1gefmbn32dn82f2i5@4ax,com ...
> On Sat, 19 Apr 2008 12:34:43 +0200, Volker Bartheld
> <dr_versaeg@freenet.de>
>
> http :// www .crocker,com /~mwilliams/Derestricted_path.htm
>
> Nice write up.

Thanks Mike.

My KTM 300 is getting 22mpg, whereas my ATK 260 got 30mpg. Arrgghhh....
I'm already running toward the lean-end of jetting recommendations. I've
got to wonder how much the V-Force reeds changed the baseline. As I'm
headed to Utah this week, and will be riding deep sand at a lower elevation,
I'm probably not going to experiment with leaner jetting. I'll just carry
extra gas. Mountain riding this summer will be a learning curve in jetting.

-Jeff-

Re: Big jets = fast?

On Mon, 21 Apr 2008 13:52:21 -0600, "HellSickle"
<jldnospameeney@comcast.spammer,net > wrote:

>
>"Mike W." <outofthe@emailbiz,com > wrote in message
>news:47sj04t6dhc0b1cro1gefmbn32dn82f2i5@4ax,com ...
>> On Sat, 19 Apr 2008 12:34:43 +0200, Volker Bartheld
>> <dr_versaeg@freenet.de>
>>
>> http :// www .crocker,com /~mwilliams/Derestricted_path.htm
>>
>> Nice write up.
>
>Thanks Mike.

My pleasure. Someone has to make up for Jay.

>
>My KTM 300 is getting 22mpg, whereas my ATK 260 got 30mpg. Arrgghhh....
>I'm already running toward the lean-end of jetting recommendations. I've
>got to wonder how much the V-Force reeds changed the baseline. As I'm
>headed to Utah this week, and will be riding deep sand at a lower elevation,
>I'm probably not going to experiment with leaner jetting. I'll just carry
>extra gas. Mountain riding this summer will be a learning curve in jetting.

I'm not sure if you remember it, but Gordon wrote a really nice piece on
the experimental process he followed in arriving at the famous Gordon Mods
back in the day. He posted it either here or in the XR400 group. I'm sure I
could track it down if you really wanted it. Gotta pack... later.

Mike

>
>-Jeff-
>

--
Mike W.
96 XR400
70 CT70
71 KG 100 (Hodaka-powered)
99 KZ1000P (training)
99 KZ1000P (rider)
00 Beta Rev-3

Re: Big jets = fast?

> I'm sure I
> could track it down if you really wanted it. Gotta pack... later.

Your girl just called my girl. Should see you tomorrow.

-Jeff-

Re: Big jets = fast?

On Apr 19, 5:34 am, Volker Bartheld <dr vers...@freenet.de> wrote:

> Normally, the first thing "people" do, is mount a racing airfilter, open up
> the exhaust, intake, perforate the airbox like an emmentaler (swiss
> cheese) and/or mount a $$$ aftermarket titanium/carbon muffler that adds
> another so-and-so much horsepower.

I basically built one XR250 from two bikes. Oddly, the one with the
big bore, ported head, aftermarket (loud as heck) exhaust, etc. had
appropriate jetting. Unfortunately for that bike, an oil banjo bolt
broke at high rpm with catastrophic results.

Anyone need a Supertrapp exhaust for the XR250? Scratch that, the best
place for this exhaust is the trash can.

Craig

Re: Big jets = fast?

On Sat, 19 Apr 2008 06:55:16 -0700 (PDT), Craig
<googlegroupmail@yahoo,com > wrote:

>Anyone need a Supertrapp exhaust for the XR250?
>Craig

Actually, maybe.

I'll trade you a CR500 rear wheel for it.


----
Go fast and aim for where the trees aren't.
----

Re: Big jets = fast?

On Apr 19, 9:47 pm, scrape <scrapeNOTHA...@nc.rr,com > wrote:

> Actually, maybe.

I keep forgetting to email you about this. I'd sorta like to hang on
to the header, but the muffler is of no use to me. If you need/want
it, it's yours. It's from an '88 - not sure what years it fits. 90+
had rear disk brakes and the stock mufflers changed to provide
clearance for the brakes. 96+ may be an entirely different animal.

Craig

Re: Big jets = fast?

On Apr 19, 6:34 am, Volker Bartheld <dr vers...@freenet.de> wrote:
> Hi!
>
> On Fri, 18 Apr 2008 19:00:50 -0700 (PDT), Craig wrote:
> > What is it with people jetting bikes stupid rich? If they think bigger
> > = faster, why do they stop at stupid rich?
>
> I my opinion, seems to be that this is the consequence of a series of
> misunderstandings:
>
> Normally, the first thing "people" do, is mount a racing airfilter, open up
> the exhaust, intake, perforate the airbox like an emmentaler (swiss
> cheese) and/or mount a $$$ aftermarket titanium/carbon muffler that adds
> another so-and-so much horsepower. Because those people need every single
> bit of their bike's power delivery since they always operate it at the
> utmost maximum all the time, no matter at what noise level.

Well consider that in this instance we are specifically talking about
an XR250...
I would most definitely need all it had to offer and probably a bit
more. I would use up about every ounce of a CRF 250 as well. But that
would about be my limit. I certainly don't/can't use all of my 300
very often. :) My 300 has passed every sound check it's ever been
through, but I wouldn't mind if it were even quieiter.

Re: Big jets = fast?

On Apr 18, 10:00 pm, Craig <googlegroupm...@yahoo,com > wrote:
> What is it with people jetting bikes stupid rich? If they think bigger
> = faster, why do they stop at stupid rich? Why not go for ludicrous
> rich?
>
> My XR250R is all stock, other than a small overbore (266cc), foam
> filter and snorkel removed from the airbox. Stock jetting is a 40
> pilot and 125 main. the PO had a 45 pilot and 138 main. Exhaust ports
> and header showed that it was way rich. In 40 degree weather it needed
> no choke for a cold start.
>
> Of course, the only 42 pilot I had was full of varnish. I fiddled with
> it for 1/2 hour today to get it clean and installed it. Turned out I'd
> gotten it clear, but not gotten all of the varnish out. The remaining
> bits got sucked into the carb, requiring another removal/clean. Yay.
> When I put everything away, I found a clean 42 in my toolbox. Double
> Yay.
>
> Craig

Ludicrous jetting? Hah! I go straight to plaid!

Easiest way to find something is to stop looking for it.


Dave

Re: Big jets = fast?

They are fast. My handheld gps showed 500 kts on an airliner trip back from
Colorado. That's pretty fast.

"Craig" <googlegroupmail@yahoo,com > wrote in message
news:df8ed798-4f03-49a7-8d32-c87d86d1a899@8g2000hse.googlegroups,com ...
> What is it with people jetting bikes stupid rich? If they think bigger
> = faster, why do they stop at stupid rich? Why not go for ludicrous
> rich?
>
> My XR250R is all stock, other than a small overbore (266cc), foam
> filter and snorkel removed from the airbox. Stock jetting is a 40
> pilot and 125 main. the PO had a 45 pilot and 138 main. Exhaust ports
> and header showed that it was way rich. In 40 degree weather it needed
> no choke for a cold start.
>
> Of course, the only 42 pilot I had was full of varnish. I fiddled with
> it for 1/2 hour today to get it clean and installed it. Turned out I'd
> gotten it clear, but not gotten all of the varnish out. The remaining
> bits got sucked into the carb, requiring another removal/clean. Yay.
> When I put everything away, I found a clean 42 in my toolbox. Double
> Yay.
>
> Craig

Re: Big jets = fast?

Craig wrote:

> What is it with people jetting bikes stupid rich? If they think bigger
> = faster, why do they stop at stupid rich? Why not go for ludicrous
> rich?

I once burned out a piston because I ran too lean. Rich is better.
Running is better than not running. I love tools but I hate using them :-(

--
Cheers,
Bev
*************************************************
Never argue with a woman holding a torque wrench.

Re: Big jets = fast?

On Apr 18, 10:00 pm, Craig <googlegroupm...@yahoo,com > wrote:
> What is it with people jetting bikes stupid rich? If they think bigger
> = faster, why do they stop at stupid rich? Why not go for ludicrous
> rich?
>
> My XR250R is all stock, other than a small overbore (266cc), foam
> filter and snorkel removed from the airbox. Stock jetting is a 40
> pilot and 125 main. the PO had a 45 pilot and 138 main. Exhaust ports
> and header showed that it was way rich. In 40 degree weather it needed
> no choke for a cold start.
>
> Of course, the only 42 pilot I had was full of varnish. I fiddled with
> it for 1/2 hour today to get it clean and installed it. Turned out I'd
> gotten it clear, but not gotten all of the varnish out. The remaining
> bits got sucked into the carb, requiring another removal/clean. Yay.
> When I put everything away, I found a clean 42 in my toolbox. Double
> Yay.
>
> Craig

What year XR250?

As I rememver the 96 and up were corked up pretty good and lean as
hell on top of that in factory form. Most people would uncork them
(remnove air boz snorkel and pipe end cap/insert) and bump the pilot
up one or two. The main was usually okay IIRC.