• Husqvarna Motorcycles Made In Sweden - About 1988 and older

  • Hi everyone,

    As you all know, Coffee (Dean) passed away a couple of years ago. I am Dean's ex-wife's husband and happen to have spent my career in tech. Over the years, I occasionally helped Dean with various tech issues.

    When he passed, I worked with his kids to gather the necessary credentials to keep this site running. Since then (and for however long they worked with Coffee), Woodschick and Dirtdame have been maintaining the site and covering the costs. Without their hard work and financial support, CafeHusky would have been lost.

    Over the past couple of weeks, I’ve been working to migrate the site to a free cloud compute instance so that Woodschick and Dirtdame no longer have to fund it. At the same time, I’ve updated the site to a current version of XenForo (the discussion software it runs on). The previous version was outdated and no longer supported.

    Unfortunately, the new software version doesn’t support importing the old site’s styles, so for now, you’ll see the XenForo default style. This may change over time.

    Coffee didn’t document the work he did on the site, so I’ve been digging through the old setup to understand how everything was running. There may still be things I’ve missed. One known issue is that email functionality is not yet working on the new site, but I hope to resolve this over time.

    Thanks for your patience and support!

38mm carb swap to 500XC

Old Geezer

Old Geezer

Husqvarna
A Class
If you've been following my original post of carburetor vents and starting issues, the post has kind of morphed beyond the original topic and into a "let's adapt a 38mm carb in place of the stock 40mm". So I thought I'd start a new post appropriate to the topic.

My brother the machinist floated out the idea of creating a bushing to allow the smaller carb to mount to the stock rubber flange. So not to be outdone, tonight I hammered out an adaptor made of UHMW. I managed with a hole saw, drill press, chop saw, and Dremel grinder for the fine tuning....here's the result with the piece mounted to a 38mm Mikuni that I just happened to have rattling around in a box of parts for an XLCH Sportster motor that I'll some day finish rebuilding.

The bushing is 43 ID/52 OD

DSC00702.JPGDSC00703.JPG
 
It is a lot more straight forward to use a 38 m/m reed flange from a 82 - 84 250 Husky. You will need the rubber carb to airbox boot from a 250 or 430 also, but everything is done with standard Husky parts this way! Can you let us know what jets you end up using please, as this is going to be the key element in the conversion.
Andy Elliott.
 
hva-factory said:
It is a lot more straight forward to use a 38 m/m reed flange from a 82 - 84 250 Husky. You will need the rubber carb to airbox boot from a 250 or 430 also, but everything is done with standard Husky parts this way! Can you let us know what jets you end up using please, as this is going to be the key element in the conversion.
Andy Elliott.
Click to expand...

Sure Andy, I'll post progress reports as I move forward.

I'm about the least conventional person you'll find, always putting function in front of form. Yes, I'll need to figure out the airbox side of things but for the short term, just getting this thing to run with just an old gym sock over the bell is all I'm after! Then I can start sourcing parts as you've suggested.

As for jetting, I'll most likely start with the jets currently residing in my 40mm carb. I don't know but it may be a bit rich...guess we'll see. Hoping someone will chime in that's done the 38mm swap with their 500. Throw in a different reed flange and reeds, and that would be another variable to consider when jetting. One variable at a time, or a person gets hopelessly confused.
 
you are correct on the one variable at a time as tuning is one step at a time
personally I would look for someone that's done the change and find the base jetting
carb slide cut is very critical when you change the bore size
 
Thanks for starting this thread! Yes, you can use the standard Husky parts, but gym socks work well, too. Nice work. Glad to see that I'm not the only home-machinist/hack out there.

You can't directly use the jets from the 40. It uses the 7-series needles and the AA, BB type needle jets, and the signal that it makes is different enough that the pilot and main numbers probably won't cross over either. I'd just start with what is known to be good starting-point jetting for a 430: 40 pilot, 2.5 or 3.0 slide (whichever you have for starters), R-4 needle jet, 6DH3-3 needle, and a 480 main. It will start and run with this, and you can go from there for your locale, fuel, and riding style. And as always... MORE PICS!!!
 
Remember a carb works strictly on the vacuum signal the engine sends it. It is very possible that a 38mm carb on a 500 engine may take leaner jetting and not richer than the same carb on a 430. For an extreme example, my '82 175XC has the same exact 38mm carb and it needs a 530 main, not because it needs more fuel, but because the vacuum signal is so weak. I agree to start with the 430 jetting, but be prepared to go in either direction, dont assume richer or leaner just on engine size.

I also agree a Lectron would be an excellent choice.
 
ok , i have a 38mm on my 500 and have struggled to get it to run properly but ....i have just found some info in the tech section that says ....a 1985 500 ae has a 38mm carb and has this setting :
main jet ..390
needle jet .r-0
idle jet ..45
needle.. 6dh20
needle pos ..3 from top
slide ... 2.5
air jet ...2.0
air screw ...1 1/2 turns out from fully in .
so i think i will try this after i rebuild the engine ....
 
Like I said, leaner main jet with a bigger engine. The main jet is never at max flow, and the carb has no idea what engine its on, it only reacts to the vacuum signal. Bigger engine of the same type like a 500 Husky will use a smaller jet because it will pull more fuel through the same size jet as a smaller engine like a 430. Of course none of this is absolute, but you have to be open to going in either direction when putting a different size carb on a bike.
 
I another thing to remember is the throttle cable for the 500 40mm is different then the 430/250 38mm, so it may make a major difference, so
keep this is in mind. My 84 500 had a 38mm & i couldn't get it to run right til i went back to the a 40mm

Husky John
 
ruwfo said:
I another thing to remember is the throttle cable for the 500 40mm is different then the 430/250 38mm, so it may make a major difference, so
keep this is in mind. My 84 500 had a 38mm & i couldn't get it to run right til i went back to the a 40mm

Husky John
Click to expand...
not quite getting cable thing ! or do you mean it might not fully open with a different cable ! as far as i can see its fully open with cable i have ,just never seem to of found the right setting but hopefully i have now .
 
Motosportz said:
Perfect place to start. Chasing jetting on a tired engine is never fun.
Click to expand...
not so much of a tired engine it's not done many hours since i built it with all new bearings etc about 3 years ago .....ive lost 3rd gear so its an engine strip to find out why ....bugger ....
 
Excellent input! Just what I need as I head into the unknown. I agree on the jetting needing to be leaner vs. the stock 40mm carb.

I'm sure the Lectron is a great carb but I can tune a Mikuni in my sleep, so for now familiarity trumps something different.

But first, above all else, I need to get this damn thing to fire up before wasting any more time or $$ on a carb swap. Just spent about 30 kicks of my time and pulled a muscle in my ass trying to light this bad-boy up after swapping my 40mm with my bro's off his 500CR. I got 4 or 5 good 'pops' out the silencer, but that's about it. Stator, coil, engine, and frame grounds all squeeky clean, choke on/choke off/no throttle/1/8 throttle/rock the bike/4 slow kick-throughs/kick just after TDC....all the tricks. What got her to pop was blowing through the float bowl vent tube to "bubble up" some gas into the throat. Thought that the new crank seal (stator side) that I replaced would fix things....NOT. Bike hasn't run in over 6 or 7 years and - guess what - it still doesn't run. Next I'll try to friction start it when the weather permits. Last resort I pull the jug and see if I have a ring problem or something (got huge compression, though).

Once I rectify the situation I'll move forward on the 38mm swap and keep you posted (or maybe I'll just bite the bullet and do it anyway, if it will make this thing behave). Currently pissed, driven to drink....
 
Old Geezer said:
Excellent input! Just what I need as I head into the unknown. I agree on the jetting needing to be leaner vs. the stock 40mm carb.

I'm sure the Lectron is a great carb but I can tune a Mikuni in my sleep, so for now familiarity trumps something different.

But first, above all else, I need to get this damn thing to fire up before wasting any more time or $$ on a carb swap. Just spent about 30 kicks of my time and pulled a muscle in my ass trying to light this bad-boy up after swapping my 40mm with my bro's off his 500CR. I got 4 or 5 good 'pops' out the silencer, but that's about it. Stator, coil, engine, and frame grounds all squeeky clean, choke on/choke off/no throttle/1/8 throttle/rock the bike/4 slow kick-throughs/kick just after TDC....all the tricks. What got her to pop was blowing through the float bowl vent tube to "bubble up" some gas into the throat. Thought that the new crank seal (stator side) that I replaced would fix things....NOT. Bike hasn't run in over 6 or 7 years and - guess what - it still doesn't run. Next I'll try to friction start it when the weather permits. Last resort I pull the jug and see if I have a ring problem or something (got huge compression, though).

Once I rectify the situation I'll move forward on the 38mm swap and keep you posted (or maybe I'll just bite the bullet and do it anyway, if it will make this thing behave). Currently pissed, driven to drink....
Click to expand...
what is timing set at ! mine was a complete bitch until i retarded it slightly , now doesnt kick back quite so much and a little easier to start .....also try plug cap mine didnt seem to like the one i put on tried a different one and hey presto ...
 
mr stainless said:
what is timing set at ! mine was a complete bitch until i retarded it slightly , now doesnt kick back quite so much and a little easier to start .....also try plug cap mine didnt seem to like the one i put on tried a different one and hey presto ...
Click to expand...
I retarded the timing a bit to 2.0mm btdc vs. the stock setting of 2.8mm. Took off the plug cap and cut off a bit for a fresh end on the wire, sanded and cleaned it. Plug is gapped at .020. No kick back (hey, if it would do that I would at least be getting somewhere).
 
If it has not run in that long make sure the crank is not full of fuel. Take the tank off and flip it upside down on the handlebars and turn the engine through to pump out any fuel if you have to, but make sure there is not a big puddle of fuel in the crank.
 
Kartwheel68 said:
If it has not run in that long make sure the crank is not full of fuel. Take the tank off and flip it upside down on the handlebars and turn the engine through to pump out any fuel if you have to, but make sure there is not a big puddle of fuel in the crank.
Click to expand...
Good advice. Did that because the last time I did try to start it the float bowl stuck and overflowed into the crank. I managed to snake a hose through the intake side and down between the crank halves and sucked out about 1/2 ounce. Then left the hose in and hooked up my air compressor and blew air for about an hour to evaporate any residual fuel. Dry as a bone.
 
mr stainless said:
not quite getting cable thing ! or do you mean it might not fully open with a different cable ! as far as i can see its fully open with cable i have ,just never seem to of found the right setting but hopefully i have now .
Click to expand...
What i'm saying is the 500 40mm throttle cable is NOT the same length as the 38mm throttle used on the 250/430, i found this out when a change
my 500's 38mm carb to original 40mm. The 38mm cable is shorter so it doesn't move the slide like it should have, so there maybe a problem
going the other way too.
 
Go to Husky Club CD #32 and your 38mm jetting specs are there on Allen McKays 82 CR500 . George Earl help him with them . This is on this site under Vintage and Ref. Tech . It's news letter #32 . I have talked to George about this conversion before and he says it make a would of different in the engine riding and starting it . When is the last time this bike has had crank seals installed as this is a big thing on these huskys . And use the husky rubber manifold instead of the sleeve .
 
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