Author Topic: 38 vs 42.5 mm (Read 4077 times)

cworobec · « **Reply #25 on:** November 21, 2013, 11:25:50 am »

I don't find a problem with the low end power on mine either, it's great all around, could just be my engine set up, but the power is always and I am not waiting on it to spool up.

Nopick · « **Reply #26 on:** November 21, 2013, 12:57:56 pm »

My Lectron / Mikuni experience is with a 42.5 Mikuni vs. a 44 Lectron so not a major size difference. Lectron = suckage, Mikuni = nice snappy performance!

Gillio · « **Reply #27 on:** November 21, 2013, 04:07:45 pm »

I had Pete bore my 42.5. It runs and responds good. I never ran it when it was a 38, so I have no input on that part. He did epoxy around the engine side to seal it up. Oh man are they thin! But strong. My .02

Stpltn250r · « **Reply #28 on:** November 21, 2013, 04:16:10 pm »

I have a standard 48 Lectron on my zilla. Has a Packard pe7 needle for alky. I purchased Lectron air fuel gauge to set the needle. It idles perfect and has great throttle response. I like mine. I found it for 150 bucks. Was set up for gas.

GrkGuy · « **Reply #29 on:** November 21, 2013, 06:27:32 pm »

yeah cant bitoch about the 42.5 stock carb, it does run very well with it.
bike is very crisp with it, you hit gas and it responds right now.

Alkyzilla · « **Reply #30 on:** November 21, 2013, 06:50:56 pm »

My VM44 doesn't take long to "spool up" either....ask Q

Buckeye513 · « **Reply #31 on:** November 21, 2013, 07:02:22 pm »

Dale I imagine you've run a 41.5 tm38 at some point is there a noticeable power gain difference switching to the vm44?

Zilla273 · « **Reply #32 on:** November 21, 2013, 07:11:34 pm »

I thought my pwk 41 had excellent response. That was about it though lol, im goin with the vm44 next spring and putting the pwk on the 2fiddy

Rainman56 · « **Reply #33 on:** November 21, 2013, 09:35:26 pm »

Guess it all preference and whether whatever carb you run is setup properly.Like others I love the Lectrons for the 250 and 500,once dialed in I found they perform better all around than any other I,ve ran.Never ran a "reworked" Mikuni though.

Alkyzilla · « **Reply #34 on:** November 22, 2013, 03:50:17 am »

Quote from: Kennerz on November 21, 2013, 06:59:29 pm

Is that the alcohol version Dale?

I run them in both gas and alcohol applications.. 44's and the 46's.

Quote from: Buckeye513 on November 21, 2013, 07:02:22 pm

Dale I imagine you've run a 41.5 tm38 at some point is there a noticeable power gain difference switching to the vm44?

On my hard running dune motors, big and small reed, doing this carb swap only,.. . changing nothing else.., there is a gain only in the UPPER rpms 6500+ of 5-7%.

IMO If your not in a situation where you run at high rpm for very long the bigger carb isn't really needed. If your constantly just shifting gears speeding up slowing down your not going to benefit. The 41.5 will give a snappier response..goes a little further on fuel too...I'm running one on the "girlfriends" (ex..

) bike we dynoed for the last pipe comparison, its in the 70's hp, great to ride. Look in the dyno section.

All the carbs mentioned in this thread are good and will run well if their set up right for your combo...proper tuning is the key.

Make sure whatever your working with isn't full of worn out pieces, especially the Keihn stuff. Makes tuning a real pain..also if your mains, needles, needle jets all that stuff rolls around in your tool box in back of the truck between tuning sessions they will NOT be the correct size when you go to use them!! I learned that many years ago the hard way with a beat up main jet. That brass stuff is soft and fragile.

Buckeye513 · « **Reply #35 on:** November 22, 2013, 04:03:00 am »

Dale do you run that UFO gizmo on your vm44? I think I'm going to buy a 44 and switch to it for when I'm drag racing and keep my 41.5 for the trails and all other riding. I do agree the 41.5 has very crisp and snappy throttle response, everyone who took my bike for a spin a couple weeks ago couldn't believe how responsive and quick the power came on.

Alkyzilla · « **Reply #36 on:** November 22, 2013, 04:17:41 am »

UFO is a waste of time...expensive dyno time. Maybe you want like to buy a couple at half price to try for yourself?? one is lightly used.. the other still packaged.

Buckeye513 · « **Reply #37 on:** November 22, 2013, 05:08:28 am »

Ufo's or vm44's??

Motoman991 · « **Reply #38 on:** November 22, 2013, 06:24:20 am »

My VM44 has that UFO plastic piece. I bought it right when I got the carb. I don't know if there is a difference between having it and not having it. I wouldn't know about expensive dyno time, my buddy never charges me lol.

Rainman56 · « **Reply #39 on:** November 22, 2013, 07:23:47 am »

The UFO,s are supposed to help throttle responce.I,ve never run them but if Dale says waste of time I,d tend to believe him with all the testing/tuning he,s done.

Buckeye513 · « **Reply #40 on:** November 22, 2013, 08:23:52 am »

When you going back up to visit this buddy Motoman?

PowerStrokin · « **Reply #41 on:** November 22, 2013, 01:24:11 pm »

Quote from: Rainman56 on November 22, 2013, 07:23:47 am

The UFO,s are supposed to help throttle responce.I,ve never run them but if Dale says waste of time I,d tend to believe him with all the testing/tuning he,s done.

When I bought and setup my vm44, I bored it to 46mm and put the UFO in it right off the bat. There really doesn't seem to be any way to get it tuned right on the bottom end with the UFO in it. It is pig rich and lazy. I primarily just drag race the zilla, so I have tolerated it. If I had it all to do over again, I wouldn't have ever messed with the UFO. One of these days I'm going to get a new slide and start over again on tuning it.

Dale or Jerry, do you guys think the slide could be salvaged after being modified to accept a UFO? I could plug the bolt holes easy enough, but I'm afraid the cutaway would never be right.

Q2W · « **Reply #42 on:** November 22, 2013, 03:06:14 pm »

Jerry surprised everyone when he commented saying the UFO mod was snake oil. I'd imagine it was from testing on one of Dale's Bikes.

Alkyzilla · « **Reply #43 on:** November 22, 2013, 03:37:18 pm »

Quote from: PowerStrokin on November 22, 2013, 01:24:11 pm

Quote from: Rainman56 on November 22, 2013, 07:23:47 am
The UFO,s are supposed to help throttle responce.I,ve never run them but if Dale says waste of time I,d tend to believe him with all the testing/tuning he,s done.
When I bought and setup my vm44, I bored it to 46mm and put the UFO in it right off the bat. There really doesn't seem to be any way to get it tuned right on the bottom end with the UFO in it. It is pig rich and lazy. I primarily just drag race the zilla, so I have tolerated it. If I had it all to do over again, I wouldn't have ever messed with the UFO. One of these days I'm going to get a new slide and start over again on tuning it.

Dale or Jerry, do you guys think the slide could be salvaged after being modified to accept a UFO? I could plug the bolt holes easy enough, but I'm afraid the cutaway would never be right.

If running a UFO you need to run a smaller pilot, that could be your rich issue off the bottom. I put that stuff way back on the shelf after testing and don't recall the exact recomendations but we did go through all that during testing. I was disappointed, in theory it should have been an improvement. BUT it didn't hurt anything.
As far as the slide, yes plug the holes..JB weld or something..if the cutaway hasn't been modified shouldn't be an issue.
I like running the Aluminum slides..buy for about $80 I believe from Sudco. The 2.5 cutaway is what I'm running on my stuff.

Jerry is out for a couple days.. don't think you'll see a response from him till next week.

PowerStrokin · « **Reply #44 on:** November 22, 2013, 04:24:12 pm »

I've got a 22.5 pilot in it, and a 7dh3 needle on the leanest setting. I think a 20 is the smallest pilot, which I played with, but it starts and idles better with the 22.5. I need to play with a 7dh2 and see if that helps. I'm sure it would. It's biggest problem is from 1/8 to 3/8 throttle. It'll load up pretty bad in that range.

Alkyzilla · « **Reply #45 on:** November 22, 2013, 09:46:42 pm »

I'm running 7DH3 needle.. check your needle jet.. mine is an AA0. That really cleaned things up vs the AA5. Adjusting the Idle tells you a lot about the pilot size but also listen for the "ring ding ding ding" after a high RPM throttle blip... if your hearing that its a lean condition caused by to small a pilot jet and can hurt the motor.

PowerStrokin · « **Reply #46 on:** November 22, 2013, 10:41:30 pm »

I had my needles backwards in my head on my last post, so I modified it. I'm running the 7dh3. I want to try the 7dh2, since it is leaner. I screwed up when I originally bought my carb and ordered the snowmobile version. I've had to change so much crap around to get it to work right. I've lost track of a lot of stuff. Being a snowmobile carb it had the 7dh2 needle originally, but I have since lost it.

I researched the differences in the two versions of the carbs and noticed the snowmobile carb had a 0.7 air jet and the bike version had a 0.5 air jet. So I went to order the 0.5, but sudco didn't have it when I tried several years ago. So I'm curious if that is part of the problem also. The thing is, I have never found clarification as to which air jet is leaner. I am certain that a physically bigger air jet is leaner, but the scale could be inverted, for all I know, to save confusion, since larger numbers usually indicate richer in a carburator. (If that makes any sense)

So which way is it? Is 0.5 richer or leaner than 0.7?

Frank · « **Reply #47 on:** November 23, 2013, 05:00:40 am »

Nopic !
Please tell me the exactly jettings of the 42 mic .
I will build me for my self in Germany ,
I think make savings for the shipping costs..
Cheers Brother

Nopick · « **Reply #48 on:** November 23, 2013, 08:15:40 am »

My engine is an 89 small reed with 500 Fanatics HRD porting. The intake is a Honda 250r air filter without an air box. Stock ported intake boot with a stock cage and Boyesen reeds. Stock filter to carb tube. Exhaust is a Q V2.

Carb is stock other than the bore as far as I know. I am not aware of Q making any modification to metering circuits.

1200 feet elevation
70 - 90 F Temps
450 - 460 main
25 or 30 pilot
Airscrew ~1.5 turns out from seated
Needle clip on the third position from the top

Frank · « **Reply #49 on:** November 23, 2013, 10:05:18 am »

And the needle jet 6dk3 ?

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Author Topic: 38 vs 42.5 mm (Read 4077 times)

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