• Husqvarna Motorcycles Made In Sweden - About 1988 and older

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Mikuni 38mm flatslide carb

Bigbill

Bigbill

Husqvarna
Pro Class
I just picked up a mikuni 38mm flatslide carb from a 85 250cr husqvarna. Down the road I'd like to compare the round slide, flat slide and the lectron. I know from what's said here the lectron is better. But the stock 38mm round slide vs flat slide.
Then install the UFO into the round slide to see how close it is to the flat slide.
What do you think? Has anyone tried the UFO in the round slide mikuni carbs yet?
 
I have a 38mm flatslide I got with some stray ITC Ohlin shocks and a set of 1987 EVO forks. I have yet to use it, it may work on the 430WR I am building because it came from an 87 430XC he was parting out
 
It is a pretty safe bet by round slide you mean the VM Micuni that came on these things. An 1985 stock flat slide most likely is inferior to a more modern one. The 38 and 39 Keihin pwk will force fit into the 38mm micuni rubber manifold and that is what I would do. I have used a micuni from 2002 (flat slide) and think the keihin would be more prefered by mechanic types. The old ones have needle jets, the newer ones seem to just use a lot more needles to choose from. I have seen needle stashes in little containers for the Lectron carbs. I am not sure how much to believe the stuff on the internet that you don't need a bunch of needles to find the right one.

The VM round slide micuni has a heavy brass chrome plated slide. this can vibrate the bore it rides in larger. The idle stop also can give out. A good condition one probably would serve well for our purposes.

Again I will note the dual shock bikes that used vm micuni used longer carbs than the mono shock ones of this section and any newer stuff I am aware of.
 
Fran, Bill is talking about the TM38mm flat side mikuni. it came on cr's and xc's of that era. 85/86/87
 
wrx said:
Fran, Bill is talking about the TM38mm flat side mikuni. it came on cr's and xc's of that era. 85/86/87
Click to expand...
Thanks for the letters, I got one on a 360 hillclimber I bought I was instructed the bike was set up perfect and don't touch anything. I changed the frame pipe and carb and the AMA changed the classes. It may well be better than the round slide I put on it. They really had "ported" the inside of the reed cage. It had a sock type air filter. I went to an airbox.
 
fran...k. said:
I have seen needle stashes in little containers for the Lectron carbs. I am not sure how much to believe the stuff on the internet that you don't need a bunch of needles to find the right one.
Click to expand...

If you tell us exactly what you are running bike and mod wise and what type of terrain and conditions we (motosportz/Lectron) can pretty much nail it. I have sold over 400 carbs and very few rods. Several rods can also work in one bike depending on what characteristics you are looking for. Kind of like changing 2 stroke pipes.
 
The lectron has different tapered needles? It doesn't have jets? Do I understand this correctly there's a flow valve adjustment for the proper gas flow? You tune the carb to your engine size and air flow?



I have dialed in a 40mm mikuni round slide with a UFO and changing the needle jet to a leaner one on the last 390cr model. After proper jetting the bike ran great not for the faint hearted.
 
Motosportz said:
If you tell us exactly what you are running bike and mod wise and what type of terrain and conditions we (motosportz/Lectron) can pretty much nail it. I have sold over 400 carbs and very few rods. Several rods can also work in one bike depending on what characteristics you are looking for. Kind of like changing 2 stroke pipes.
Click to expand...
The guy with the needle or rod stash had a honda cr 500.

Just for the purpose of discussion I have a dual shock 1982 to 1984 bike with the matching airbox. I have both 38 and 40mm rubber manifold and airbox rubber. What do you have to fit in between?
 
Bigbill said:
I have dialed in a 40mm mikuni round slide with a UFO and changing the needle jet to a leaner one on the last 390cr model. After proper jetting the bike ran great not for the faint hearted.
Click to expand...
I could be wrong but I wonder if that reed cage could really be a good match to a 40mm carb.
 
i really dont want to sound rude but comparing the carbs mentioned sounds like a colossal waste of time with hours of jetting with no real purpose. i personally would stick with the mikuni vm unless you are going to upgrade to the simplicity of the lectron. yes virginia, there are no jets. the mikuni vm is a great easy to jet popular carb and its a classic. if i am going to get rid of it im going to make it count and get a real upgrade, not a slightly better (or worse) tm.
bill i really suggest you go to lectrons site and do a bit of research, then ask some questions here at the cafe if you have any.
 
If you don't have an airbox changing jets is much easier.

Is the 1985 tm micuni the same as what is on my 1998 125 and 2004 250 both two strokes? I thought the one I mentioned earlier looked different though I haevn't looked at in years. The Lectron, though I don't know how things change over time were very popular at hillclimb events perhaps 10 years ago, not so much lately, of course two cycle engines here.

What is the UFO device is it a horizontal plate?

Whatever comes on a Yamaha yz250 and Ktm 250 sx is likely the best choice, my opinion. Maybe see what comes on trials bikes if that is more your style. I never mounted and ran a lectron but have spent the time to understand the needles for the Keihin. It is a crescent slide but mine is like 10 years old by now.
 
your later two strokes fran have tmx carbs, altho they likely have "tm" embossed on the top rear of the carb. the old tm carb is much different. my 95 360 had the tmx. it ran and started well but its on a different level with lectron. very nice to not have overlapping circuits affecting each other. i thought it was hype but it was kind of a "zen" moment for me.
lectron has enjoyed a resurgence lately with many gas gas, husky, and ktm users making the switch. a drawback to the lectron is the lack of a brute "hit" when first opening the throttle. sx or mx riders tend to not like this, but its a welcome feature everywhere else, especially the woods. they tend to pull very hard at upper rpms. the way it meters at different throttle openings is amazing.
 
Bigbill said:
I just picked up a mikuni 38mm flatslide carb from a 85 250cr husqvarna. Down the road I'd like to compare the round slide, flat slide and the lectron. I know from what's said here the lectron is better. But the stock 38mm round slide vs flat slide.
Then install the UFO into the round slide to see how close it is to the flat slide.
What do you think? Has anyone tried the UFO in the round slide mikuni carbs yet?
Click to expand...



to compare them you need to jet them correctly then take them off and swap them, if you have that kind of time i"ll read it
the round slide vs flat is simple, the flat slide was about snap, motocross riders wanted a quicker response and the flat slide provided it
but,,,, the round slide offers a better tuning all around design for technical riding
they both have their place, technically the Lectron is a flat slide, the difference is the metering system
 
fran...k. said:
If you don't have an airbox changing jets is much easier.

Is the 1985 tm micuni the same as what is on my 1998 125 and 2004 250 both two strokes? I thought the one I mentioned earlier looked different though I haevn't looked at in years. The Lectron, though I don't know how things change over time were very popular at hillclimb events perhaps 10 years ago, not so much lately, of course two cycle engines here.

What is the UFO device is it a horizontal plate?

Whatever comes on a Yamaha yz250 and Ktm 250 sx is likely the best choice, my opinion. Maybe see what comes on trials bikes if that is more your style. I never mounted and ran a lectron but have spent the time to understand the needles for the Keihin. It is a crescent slide but mine is like 10 years old by now.
Click to expand...

The UFO is a plastic round wedge that screws into the bottom of a round slide carb. It eliminates the gas flow that stumbles under the round slide carb.
 
The early Mikuni flat slide (TM) is not an improvement on the VM. The later flat slide (TMX) is better but it is not legal for vintage racing.

The Lectron has no jets unless it has the power jet circuit, and that uses a Mikuni pilot jet. The taper of the needle regulates all fuel supply (other than if it has a power jet). There is no need to compare the Lectron to any Mikuni, it is far superior, and it is significantly better than the current best mainstream carb, which is the Keihin PWK.
 
Kartwheel68 said:
The early Mikuni flat slide (TM) is not an improvement on the VM. The later flat slide (TMX) is better but it is not legal for vintage racing.

The Lectron has no jets unless it has the power jet circuit, and that uses a Mikuni pilot jet. The taper of the needle regulates all fuel supply (other than if it has a power jet). There is no need to compare the Lectron to any Mikuni, it is far superior, and it is significantly better than the current best mainstream carb, which is the Keihin PWK.
Click to expand...

Right or wrong the extention of this logic is in the six or so years BMW owned Husqvarna motorcycles they chose to use something far inferior. Was that Meo guy able to win his title with the stock carb? ( I know he had some impressive finishes on the two stroke huskies even if the title was on a four stroke, don't follow it that close)I know they didn't use the stock suspention just from examining pictures on the internet. USA Off road stuff.
 
I really dont care what they used, if it was not a Lectron it was inferior. I either have, or have had, motorcycles with every currently available carburetor, almost all the carbs used in the past, and nothing is even close to a Lectron, except for that company that makes the billet copies of the Lectron and charge 3 times more for it. Unless you have ridden a bike with a properly tuned Lectron you really cant understand just how much better they are than everything else out there.
 
I have never had a bike with a lectron on it. I bought one at a NETRA auction thing at the awards night thing for $10 No one else bid and sold it for $10 a few years later and that must have been 15 years ago. I think it was a 36 mm one.

Since Motorsports doesn't seem intrested in answering, do they have one the right length for the dual shock set up? One to fit into the rubber parts for the 40/44mm round slide?
 
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