mikuni vm 16

​
Well guys, played with the air screw, its 2 1/4 turns out & running fine, with motor & pipe up to temp there is no 4 stroking & its very responsive. Good plug color. Its autum at the moment. I have a 75 main & 27.5 pilot if needed in winter when the air is denser & a 70 main jet & the 25 pilot thats in now if needed in summer's rarer air but I think as is now'll do for summer. This is a great carb for these motors, & so adjustable. I'll order a pull start from rocksolid next week. The coupler is attached to the magnet & the pullstart unit is used instead of the magneto cover. They also have reed cage assemblies now so,, maybe soon. Cheers
 
​
Tip. These carbs r 4 rotary valved 2 strokes & 4 strokes & have bleeder holes in the needle jet. Air enter thru these & mixes with fuel. If u have trouble tuning in the 1/4 to 3/4 throttle range, remove air cleaner & block off the drilling at the very bottom of the air intake to stop this happening. Cheers
 
ivan H said:
​
Tip. These carbs r 4 rotary valved 2 strokes & 4 strokes & have bleeder holes in the needle jet. Air enter thru these & mixes with fuel. If u have trouble tuning in the 1/4 to 3/4 throttle range, remove air cleaner & block off the drilling at the very bottom of the air intake to stop this happening. Cheers
Click to expand...

My old CNS from Spookytooth has those bleeder holes in the needle jet but I never knew anybetter tell now. I'm gona have to try that in a bit since I can never get 1/4 to 3/4 and WOT at the same time. This might actually explain alot. If not I might be buying VM16 which is why at looked at this thread in the firstplace. The Dellroto SHA just don't sound right for me, I want something I can tune in all ranges. I also believe my CNS is a clone of a Mikuni for a Yamaha PW80 and looks like a v3 without the capped air screw. The Mikuni jets for the PW80 and VM series are the right length but I'm just gona have to order one to find out if the threads are right. So it just might be a Mikuni clone.

What do you suggest to block the hole? All I can think of right now is cork-rubber and Seal-All or just Seal-All.
 
​
U could use lead to block it, or just roll up some teflon thread tape & push in there, tht way if it came out & got ingested it wouldnt do harm. Order VM16 from mikuni corp so u get genuine, I've herd some off Ebay r Chinese made under license. All jets r available, & needles with different tapers & slides with different cutaways. They have 3 mounts available, flange, spigot or clamp. Clamp is designated VM16-516, I think. I'll check when I get home & let u know if different. Cheers
 
​
BTW, mikuni main jets r not a straight drilling. If u look thru from the threaded end they have a venturi shaped profile. Pilot & main jets come in increments of 2.5, which is 0.25mm. The VM16 u want is designated either VM16-516 or 519, but I think its 516. The other 2 mount style carbs have completely different designation so if u go 2 mikunicorp's web page u'll have no problem getting the right one. Cheers
 
Well I'm gona try the cork rubber gasket stuff. I cut a square just bigger than the hole about 1/4inch long. If it gets sucked it shouldn't do any damage unless it turns to goo. Should at least work for testing. I think this motor china girl is about done anyway its 2 years old with a couple thousand miles and I'm just waiting on seal for the new one. I'll update after the test ride to the store, its a 2 mile round trip if that.
 
​
Hi Stormtrooper, u may have 2 raise the C-clip on ur needle, depending on if it was running lean or not between 1/4 & 3/4 throttle as with the air blocked off it'll b richer in that range. Hope it works out 4 u. Cheers
 
It did make it richer but I'm still zeroing in on the main jet which seems to effect 1/4-3/4 not just WOT on this suspected oem version clone. Before a resent tear down to deal with a chirping bearing and crank seal leak, I had it running good. It just didn't like mid range much no matter where I put the c-clip and I have shims that came with a fishing real that give two more spots between each of the five slots on the needle. I'm starting to suspect my new base gasket is a bit thick since it doesn't crush like the stock one did and has changed my timing a bit, but that's a topic for another thread.

Now back on topic the two Mikuni sites I found state they do not sale direct and have links to distributors that don't sale direct either. So it looks like I'm gona have to call one of the local shops listed as dealers from one of the distributor links to be safe but know those places in my area there gona say $150 or more so might have to take a chance with Sears since they actually list one on there site and have it on Amazon.

Also the Mikuni catalog says the VM16-159 is the clamp on but it doesn't say what type the 516 is. I can't find any other numbers for the VM16 on the Mikuni site. I also cant find the 159 anywhere other than Sudco or the catalog on the Mikuni site. Might just have to call Sudco and hope they deal direct at a decent price when I have the spare money. The one at Sears lists it as a VM16-516 but shows a picture of a BN lol.

Sorry I tend to ramble a bit sometimes.
 
Mate, dont pay that much. I paid $88 & thats 4 genuine. Go 2 mikunioz.com.au. Even with freight u wont pay much more'n $100 & u'll wait less than 2 weeks 4 it 2 arrive. I'll b home in a few hours & check that designation 4 u & post it. Cheers
 
​
Ok Stormsorter, (sorry 4 calling u stormtrooper b4),, its VM16-519, written on the top of the right hand side (when sitting on bike) boss that the clamp bolt passes thru. I paid $88 when our $ was better'n ur's & now ur's is slightly better'n ours. The price still same, a friend just ordered 1, from [email protected], so dont pay too much mate. Cheers
 
​
Hi Stormsorter, how'd u go with it? Mate, put ur C-clip in middle & tune main jet 1st @ WOT, then while @ running temp (if its got pilot jet) put air jet adjust about 1 1/2 out wind idle screw 2 very fast idle & slowly back air adjust out or close, looking 4 highest rpm & reset idle & redo air screw, then do C-clip by plug chop. Never remove plug until motor is cool, so u'll need 2 have a couple of goes at tuning. Cheers mate
 
Last edited:
Blocking the bleeder hole seems to have helped but its hard to tell since I messed up a bit putting in new crank seals. They starting to leak air under load already, didn't have a socket the exact size and took a chance. When I get my new ones I'm gona drill out a big washer I have so I don't indent the center of the seals a bit this time. That and I'm gona be a bit of a guinea pig and try replacing the 14.8mm ID seals with better double lip NBR's that are 15mm ID. I'll post an update once I get to do some testing without an air leak.
 
Hi Stormsorter, yeah, leaking seals will make it impossible 2 properly tune ur carb as they leak under vacuum & compression. B sure 2 wet the lip of the seal with a little oil b4 fitting. I fitted mine with just my thumbs, but I did have the cases apart at the time. Hope the double lip seals work 4 u. Cheers
 
The lower con rod has more play then I like but I think it may have been that way since new. Lots of left and right play but no up and down. Its about 2 years old so who knows how much longer before the bearing goes. That and the micro scratches in the cylinder around the ports either from carbon deposits or more likely from forgetting I took the cap off the inlet to the venturi near the filter for about 2 weeks.

Though I'm pretty sure plugging the bleeder hole is gona help. It was always lean in mid if I had the jet close to wot even with the clip on lowest notch of the needle. Now with the bleeder plugged I have the clip in the middle and have good mid range and after about a block or 2 at wot the air leak kicks in. So it seems like it just might solve that one problem I had with this carb. I'll should know for sure once I get rid of the air leak again. The micro scratches might be at play to so I may not be completely certain tell I switch to the new engine.

I'll put the new engine on the bike once I know the 15mm seals work. The old engine gets to be a test subject for the seals. Then It'll be used as a test subject again for building the Giant Stiletto I picked up for $30 last year. A little rusty, no chain guard and a worn out grip shifter but still a great find, I didn't even know what it was at the time.
 
Last edited:
Almost forgot, once I have the spare cash I'll buy the Mikuni since I have 2 engines and one carb. Then I'll get to see if the jets fit. I know they're the same length but I have no idea if the threads will match. As I'm pretty sure the old Spookytooth CNS I have is a clone of an OEM version of the Mikuni VM16 for a Yamaha PW80.
 
Hopefully it all works out 4 u. I just measured an old seal ID 14.5mm with calipers, so I guess we'll c how it goes. Mikuni clamp ID is 25mm, but they come with plastic shim/spacer with ID 21mm. O-ring ID 21mm being interferance fit. I read somewhere tht the dellorto main jets will fit in these VM mikuni's but havent checked. The Mikuni dealer here told me about blocking the air to the NJ bleeders if having trouble tuning, said they do the same with the TM series carbs on 2 strokes. Cheers
 
Hi guys, well after clarifying & setting proper squish clearance 4 RSE head & adding header length 2 SBP chamber I was running pretty lean. After waiting on jets then a week of rain 2 clear I got into it 2day. With 77.5 main jet & C-clip in center position its starting 2 run well. Still a little 4 stroking mid to 3/4 throttle so maybe go up 1 position with the C-clip. Hesitates up to 1/4 or 1/3 throttle so I'll go up to 27.5 pilot jet, c how it goes. Soon as its properly dialled in I'll get a bit of pipe bent up the same length as is now & get the pipe all welded up. Cheers
 
Last edited:
You must log in or register to reply here.
Back
Top