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Old 12-29-2010, 06:36 AM   #16
stainlesscycle
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Quote:
Originally Posted by Armchair View Post
So you have little to no experience with piston port and early reed valve 2 stroke motors?

BTW, the price is for a plug and play carb, no trial period of selecting the idle jet, main jet, slide, needle, etc. to get the bike to run correctly.
yep, no experience at all.
just put these on in the last 2 months.
32mm on 200cc bultaco
36mm on 2 different 250cc bultaco
34mm on 175 can-am (rotax)
36mm on 250 husky

there's no such thing as a plug and play carb. there's so many variables. sure it might be close out of the box, but most likely you will still need to jet.

i'd have to look, but i still think 30mm is small for 360cc..i am not a believer in bigger is better, i'm not saying go bigger just randomly. we don't know if it's a stock motor with stock jets,reed and pipe. we don't know elevation and temperature. there is no hard and fast rule for what carb size will work best. i have on occasion gone with a smaller than stock carb if original carb was obviously too big, and i wanted to get more intake velocity. i do realize it's a trail bike that may have been restricted a bit with carb size...

and vintage iron i believe is charging $199 (unless it's a typo) according to their site, and it appears to be a stock jetted carb for that price. that's more than DOUBLE the going rate. i got nothing against vintage iron, i just think that's ridiculous pricing. even hugh's bultaco (not known for being cheap) will sell pre-jetted (foir your model) mikuni's for $150ish. that's with a non standard slide and needle. i don't buy them pre-jetted to someone else's guesstimation. i buy them stock jetted and go from there. maybe vintage iron has done some research and figured what works best for a dt360 - but i seriously doubt it. there's just not a lot of people changing carbs on a model as uncommon as this. i have worked on several rt-3's and know that they're set up goofy stock.
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stainlesscycle screwed with this post 12-29-2010 at 06:54 PM
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Old 12-29-2010, 07:19 AM   #17
davevv
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From page 105 of the service manual, carb specifics:

Manufacturer/model = Mikuni VM30SS
I.D. number = 44560
Venturi size = 30mm
Main jet = #180
Needle jet = 0-8
Jet needle = 5EJ8
Cutaway = 3.0
Pilot jet = #50
Starter jet = #60
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Old 12-29-2010, 09:51 AM   #18
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Good reply Stainlesscycle.

My reply was in response to the OP and his appearent lack of knowledge so as to give him an easy solution. Too bad he does not say where he is located as I'm sure one or two members here could come over and help out.

I have bought several carbs from Vintage Iron, the last one was for a 1972 CZ400. Like the others before it, it was plug and play. YMMV.

I hope the OP sees this and replies.
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Old 02-14-2011, 06:47 PM   #19
Kevin 007 OP
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Im in Nelson B.C Canada.
Well I just had this bike bored 2nd oversize with a NOS Wiseco piston kit in it, new reeds etc... I had the carb completely apart again with thorough cleaning and the problem is still there.
The current jetting has always been the way it is and the bike is from the area...no altitude changes. So should I go and get a new needle and needle jet and see where that takes me? Im guessing my problem lies in that area. Idles great..mid range to WOT is great; just that one certain trouble spot at low throttle.
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Old 02-14-2011, 09:13 PM   #20
stainlesscycle
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when you change the needle position does the problem move to a lower/higher rev range?
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Old 02-15-2011, 05:36 AM   #21
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I don't know how to adjust the needle position.
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Old 02-15-2011, 06:34 AM   #22
stainlesscycle
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remove carb top. take slide out.
remove throttle cable from slide.
remove spring, remove retainer plate (may or may not have one - depends on carb model)

push needle out of slide from the bottom.
there's a clip on the needle.

which position is it in? needle has either 3,4, or 5 grooves in it. moving the clip UP lowers the needle and leans it out. moving the clip DOWN raises the needle a richens it.

here's a pic of a needle in position 4 - the richest position on this particular needle.

you mention it has problems at 1/8-1/4 throttle ? that's either pilot jet or needle positon/taper USUALLY. it could be airscrew too....

you're in canada. it's probably cold there :) i'm betting richening up the pilot one step, and maybe raising the needle up a notch will compensate for the cold. but it may be too rich when the temperature increases. you say it runs great a wot? with how cold it is it may be slightly lean on the main too. don't forget 2 strokes run the best right before they blow up :)

you need to google '2 stroke jetting' and go through the whole process. keep in mind, that your proper jetting at current temperature will most likely be too rich when the ambient temperatures increase. keep in mind it's really hard to jet over the internet.

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stainlesscycle screwed with this post 02-15-2011 at 06:51 AM
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Old 02-15-2011, 07:26 PM   #23
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Another great post Stainless!!
Ok I know which clip your talking about now...I had no idea that was its function. I will look into that ASAP, probably weekend tho.
For some reason, I think the clip is on the top notch....

The plug is always a little on the cark side however.

When you say "needle position/taper" is that what we are talking about with that clip raising and lowering the needle?

The pilot jet is new and free of crud. I have fiddled with the air screw..seems to run best when it is turned "out'' about two turns
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Old 02-20-2011, 04:44 PM   #24
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Hey stainless I I lowered that clip from the top notch, down two notches. And I think that cured it!!!!
Have not ridden it much just 100yards and back, due to the snow and cold. But if its not cured, its definitely a LOT better!! I will now have to wait till spring until I take it for a good long ride until I know for sure.

I have one more question on this machine, off topic but it wont take much, dont want to start a new thread for it.
-I want lower gears. Will it be easier to swap the front sprocket for a smaller one or the rear for a larger one? It has a 45 tooth on the back...seems pretty generic to me. SO im thinking change the front. Good idea?
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Old 02-20-2011, 05:25 PM   #25
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switching rear to larger is almost always better. significantly longer chain life. what size is the front now - 14?
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Old 02-20-2011, 05:26 PM   #26
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These years of Yamahas really didn't respond well to big carbs . The transfer ports which carry the fuel charge from the lower end to the combustion chamber are very small with not much room for enlargement via porting. Thus they were low revving torque monsters.
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Old 02-20-2011, 05:33 PM   #27
davevv
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For gearing changes, either one should work and I don't find a lot of difference in the effort either way. Changing the rear actually allows finer tuning of what you're after though. As a rule of thumb, a one tooth change on the front will be equal to about a three tooth change on the rear as far as the ratios are concerned, so changing the rear allows you to choose smaller steps toward your goal if you so desire.

The other consideration is that a smaller front sprocket will induce a little bit more wear on the chain. It's not major, but there is a difference.

Edit: Stainless answered while I was typing.
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Old 02-20-2011, 06:41 PM   #28
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Ok, I will likely look into a larger rear sproket then. Maybe a 50 tooth. I want to go quite a bit lower than what it is as the bike will be strickly a trail machine now.

Not sure what the front it. Looks pretty big to me
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1981 Honda Trail 110...best bikes ever!!!!!
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Old 02-20-2011, 07:17 PM   #29
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Well Done!!

Now this kinda thing is just where ADV shines brightest. Here's a guy in BC, Canada, looking to buy a carb to replace one that's giving him fits. Then arrives another inmate from across the whole damm continent, in a foreign country even, who helps the troubled man without his having to spend a Canadian Dime!

Sir Stainless, Iff'n ya ever make it to ride here in Colorado, I'd be honored to buy you a beer!
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Old 02-20-2011, 07:46 PM   #30
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And same goes for a stainless adventure to the great white north!
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