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Caburetor jetting

Posted: Fri Apr 22, 2005 4:04 pm
by Smuz
Now THIS promises to be a long and involved thread.

I just finished re-jetting the Weber carb in Mouser and getting some jets that I thot would work at 10,000 ft altitude. Ok, that's done. Now it's Wilson's turn.

Wilson, as most of you know, is a stock LJ10. What you may not know is that he originally came from (as far as I know) Amarillo, Texas. Mouser (another LJ10 who is not a subject of this discussion except for his donation of a stock LJ10 carb) is from Salt Lake City, Utah.

Now I live in Kansas City, which is NOT at a very high altitude (750 feet above sea level). Poor little Wilson is about to be taken up to 10,000 feet above sea level for the first annual LJ10.com meet. Carb re-jetting is a must.

So wot jets do he have, wot jets should he have, and wot freaking jets do he gonna need at 10k feet?

I guess first we gotta establish a baseline.

I got three LJ carbs from three different sources. So I pulled the main jets and checked the sizes. Here's wot I got:

carb / From / Altitude / Jet Size

LJ10 / Wilson / 3600 / 95
Lj10 / Mouser / 4300 / 85
L40 ?? / Parts / 0 / 110

Posted: Fri Apr 22, 2005 4:11 pm
by Smuz
Following this logic, an LJ10 jet for 10k feet should be in the nieghborhood of 65-70.

If anybody wants to help with this research, go out and pull yer LJ10 main jets and tell me wot they are and wot altitude yer at.

I plan to bring a buncha jets about the right size to the meet so's that people can re-jet thier vehicles at the meet.

Next pics shows where the jet is located.

Posted: Fri Apr 22, 2005 4:14 pm
by Smuz
this is the plug that gotta be taken out to see the main jet. It's easy to get to without taking anything else apart. Juss remember that there is a little metal washer. Take care not to lose it, altough it does normally stick either to the caburetor body or to the head of the screw.

Posted: Fri Apr 22, 2005 4:16 pm
by Smuz
And here is the main jet screwed into the top of the plug. The size is stamped into the top. As you can see, if'n ya looks close, the size of this jet is "110"

Posted: Fri Apr 22, 2005 4:21 pm
by Smuz
I'll be interested to hear from people as to what size jets they have and what altitude their LJ's came from.

I'm also interested in the same info from LJ20's, although I dunno if the main jet is in the same place.

Also:

I always thot this carb was a Hitachi, but the jets in mine are identical to Mikuni.

Stevec has a carb manual for these, mebbe he kin tell us.

Posted: Fri Apr 22, 2005 4:28 pm
by stevec
I'd have to check the manual - there were two different carbs on LJ10's though. I'd also have to pull the jets of my LJ10 - seems like 85 or 95 rings a bell, but it's been a LONG time since I did anything with the carb.

Looks like they're easy to get to (i.e. don't have to tear the carb apart to change it!) :cool:

Posted: Fri Apr 22, 2005 5:57 pm
by Smuz
Yeah.

I got this great big box fulla Mikuni jets. Unfortunantly the smallest size in the set is a 95.

Drat!!!!!

Posted: Fri Apr 22, 2005 8:26 pm
by Sluggo
This thread has a lot of great information and everyone else is probably REALLY greatful, but my question is... How many of you have pulled LJs out from under my nose in the Texas Panhandle while I was snoozing????

Part 2... please quit that!

Posted: Sat Apr 23, 2005 5:24 am
by Smuz
Sluggo wrote:This thread has a lot of great information and everyone else is probably REALLY greatful, but my question is... How many of you have pulled LJs out from under my nose in the Texas Panhandle while I was snoozing????

Part 2... please quit that!
Not me, oh great and annoyed one. When Wilson's owner died in 1993 (or so) his daughter took Wilson home with her to Lyons, Colorado and stored him in the back yard. 10 years later she put him on Ebay and sold him to me.

So you see that I am completely innocent of ever sneaking an LJ out from under your long and pointed nose. I would never, ever do sumpin like that. <snicker>.
:hail:


Now wot jet size is in your carb and where did it come from originally?

Posted: Sat Apr 23, 2005 6:22 am
by russmehl
How many of you have pulled LJs out from under my nose in the Texas Panhandle while I was snoozing????
Guilty as charged. I think you got to watch the dust cloud as Nemo headed North...

But that was before we knew what a swell guy you were....

Russ

Posted: Sat Apr 23, 2005 7:23 am
by Smuz
Besides, I bought Wilson about 18 months BEFORE you joined here.


Posted: Sat Apr 23, 2005 7:55 am
by Smuz
A little more info.
According to the parts manuals on this site, an LJ10 comes with a #110 main jet and the LJ20 comes with a #120. I'm gonna assume that this is a sea level jetting. That pretty well jibes with the jetting in the 3 carbs I have.

I'm gonna tentatively say that jetting for 10k feet will be:

LJ10......#70-75
LJ20......#80-85

Anybody know better or see any flaw in this logic, please jump in.

Posted: Sun Apr 24, 2005 12:44 pm
by Jimny
Sluggo wrote:How many of you have pulled LJs out from under my nose in the Texas Panhandle while I was snoozing???
A few years back I was heading down to Texas to pick up 2 LJ20's and a LJ50 BUT I barley made it into Oklahoma before my truck broke down so I didn't make it there and fixing the truck took most my money that I was going to buy the LJ's with so I never did get them. I wish now I would at least made it half way and bought the 50. If I had known back then how hard it is to get a 50 around here I would have tried harder to go get it.

WAIT! Texas has a pan handle too? I thought that was just Oklahoma.
:wink:


As for the jets for the 20's they are almost as easy to get to as the 10 is, no need to pull the carb off your rig. Here is pic from the LJ20 Service manual. Off the top of my head I don't remember what they had in them for the original size neither.

Posted: Sun Apr 24, 2005 6:27 pm
by Sluggo
Yeah, they call everything from Tulia north the Panhandle. The part that is directly south of the Oklahoma Panhandle. I can see why they call the western parts of Oklahoma and Florida panhandles, but I can't quite figure out the Texas one.

Posted: Mon Apr 25, 2005 9:23 am
by stevec
I checked the carb manual, and the main jet on an LJ10 is either 110 or 120, depending on which carb you have, so your numbers make sense smuz.

So can you get lower jets (i.e. 75), or is 95 the lowest?

Posted: Mon Apr 25, 2005 12:47 pm
by Smuz
So can you get lower jets (i.e. 75), or is 95 the lowest?
Yeah, looks like you kin get 'em all the way down to about #30. Price is prolly gonna be about $3.50 ea.

Posted: Tue May 31, 2005 3:45 pm
by Smuz
OK pipples, I'm gonna order sum Mikuni #70 jets in a day or so. Anybody that needs a jet, say so now or I won't order one.

After the totally underwhelming response to my request for jet sizes, I ain't holding my breath on this one.

Posted: Thu Jun 16, 2005 12:56 pm
by Smuz
Too late. I got mine.

Carb re-jetting

Posted: Tue May 29, 2007 3:36 am
by Myers
Looking for source and size for high altitude jets for lj20 carbs. Trying to get ready for Cooke City MT. area. Any help appreciated.
Myers

Posted: Tue May 29, 2007 4:39 am
by Jimny
I don't think we will need them there.

But if you want some just in case, then Smuz can get some.

Posted: Tue May 29, 2007 6:32 am
by tweeder
Jimny wrote:I don't think we will need them there.
10,000 feet...

for what it's worth, they look almost exactly like Holley jets...

Posted: Tue May 29, 2007 10:47 am
by stevec
Yes, we will be up close to 10,000'. You won't "need" them, but you'll want them! I didn't rejet the LJ's for the 2005 meet, but I wished I did, especially the LJ10.

Smuz, where did you get yours from?

Posted: Tue May 29, 2007 7:59 pm
by Smuz
Got 'em from a box of motorcycle jets a friend had. But when I got up to Silverton, none of 'em worked as good as the stock one.

Posted: Wed May 30, 2007 4:32 am
by Myers
Thanks for the info on carb jets. I once took a 250/ 6 cyl. chev. pickup (w/carb.) to Estes Park CO and while going up was passed by real thin people riding bicycles resulting in a double downer for a big bellied Okie.