Author Topic: vm28 vs vm30 on cl360  (Read 1972 times)

Offline crazypj

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Re: vm28 vs vm30 on cl360
« Reply #10 on: May 13, 2018, 14:11:20 »
I remember reading ? years ago when Yamaha first started using reed valves that the 'signal' was more like a fourstroke than the 'instant open' piston port which is why they went with bleed type emulsion tubes. Mixing and matching from the various models will give you exactly what you want but will get pretty expensive if you use genuine Yamaha parts. You can find specs for various reed valve models though (from 125 to 400) and see what they use for different cylinder capacities. As teazer points out, two strokes tend to be a bit richer mid to top end but you can make better 'educated guess' with more information
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Offline raptormeat

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Re: vm28 vs vm30 on cl360
« Reply #11 on: Jul 23, 2018, 02:09:57 »
feel i should chime in hillset!  back at sea level now...rebuilding top end right now due to leaky copper head gasket (kindof expected that, i dont trust copper gaskets anymore)...BUT I am putting in a wideband 02 sensor in my exhaust so i can tune my bike once and for all..still using vm28 roundslides

a few things we know:
360s like long exhausts..to rear axle ideally
there are 2 types of needle jets for the VM28s.  Bleed (leaner, good for 360 and 4 strokes, 175 Mikuni #s) and Primary (richer, 2 strokes)  which a lot of 350 racers (vm30sand 159 jets) tune with(169 Mikuni #s)...so I would say its possible to get the bike running reasonably well with either needle jet, but the other variables (exhaust, filters) also impact the Bleed or Primarys usefulness..all depends on the AF ratio..

air jets: 2mm air jets should be used with Primary type needle jets, to help atomization.  a Bleed type needle jet needs less, maybe .8mm or even stock on RD350 carbs is .5 i think...a 2mm air jet blowing into a bleed jet would be very atomized, but too lean midrange...unless you maybe richened everything up with lower float levels, a huge main, and a richer needle jet...its all a balance based on so many things...there is no perfect IMO.

filters: vstacks will let in adequate air all the time (and other stuff) so will need to compensate with a richer needle jet, bigger main, or lower float level gap, than if you had used Unis, which may be too restrictive if the small pod kind....even if we all had identical setups, 'theres more than one way to skin a cat.'

ALSO use this method of tuning. http://smellofdeath.com/lloydy/jetting.htm  Do this once u have a smooth idle. Another thing to try is use some of the most common cb350 mikuni jet setups minus 10%, so if someone used a 30 pilot on vm 30s, try 27.5, if they used 170 main Jet on vm30s, try 152.5-155 main Jet on vm28s, primary needle Jet p-5, try primary 0-8 .

not going to throw any numbers out until i start tuning on the wideband. then will get dno tested and repeat again.  AEM has weldless O2 bung kits haha. best part of the 360 is you can brat the tail with the stock rear loop and an angle grinder...no welds on my ride.

« Last Edit: Jul 23, 2018, 03:31:56 by raptormeat »
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Offline irk miller

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Re: vm28 vs vm30 on cl360
« Reply #12 on: Jul 23, 2018, 09:43:57 »

360s like long exhausts..to rear axle ideally

This is because of the CV carbs.  You negate that with the VM carbs.  And copper gaskets work well when properly annealed and installed with a layer of copper spray on both sides.