MOPED ARMY

The pmfm actually started out as a 25 mph ''b'' model and I was able to break 50 with it.

I generally followed the guide in the wiki but payed a lot of attention to the case halves.

The 25 mph cylinder has bigger transfer port windows which saves a lot of tough porting work on them. You want to raise the exhaust port by quite a bit and lower the intake by the same amount.

You can widen the intake window by a lot because the piston rings never travel over it but the exhaust can be much less forgiving so dont go too far to the left and right about 2mm either side.

The ''devil horns'' on the crankcase halves needs to be matched up and you can open them up to the pont where they will still maintain a seal.

I also milled the head by about 3mm with wetsand paper and a perfectly flat patio block and I use high quality Hondabond grey silicone for a base gasket and no head gasket.

Contrary to what has been said you can mod the exhaust with a larger exit pipe. I used an old small bottle jack pump handle and welded into the endcap and removed the first baffle then trimmed the exit pipe to fit in the upper of the three holes.

You might have better luck with an after market pipe though just nothing huge or you will have no low end.

I run high test gas in it from a station that has a seperate hose for each grade and I have advanced the timing I have yet to hear any preignition.

I am currently running a 14/14 sha dellorto and an opened up to 14mm stock shorty intake.

If you have the 25 mph engine it should come with the 10mm gurtner I hit 50 on a modified one but I had no low end power with it.

Yeah, a dellorto is definitely on my list.

I'm thinking of an sha 15:15 if I can find one on the cheap.

maybe a 14:12, only cause they're easier to find used.

It's such a nice day, I couldn't let it go to waste....

Gotta love them Dremels.

I used some silly putty I had to keep the shavings from entering the crank case. that worked surprisingly well. Only problem is that silly putty tends to "melt" or "ooze", so it's best to work in a cool space.

I still need to get in touch with my dad's friend with the machine shop to do the cylinder/ head/ intake machining. I hope it won't cost too much, I just spent $60 on tires & tubes + shipping.

-peace

nice work. putting together a very similar modified stock 50v. case matched bottom ends, ported as per wiki specs very carefully. piston skirt chopped... all the basic stuff.

havent milled head.. 3mm seems like a shit lot but if you dont have head slapping issues that sounds great.

port map _before_ porting is attached. do the math and you'll see what it'll look like after.

thinking the 16 sha is going to be too big even with a G3, might go down to a 14 just to try it. i also hear you can pop the jet holder/emulsion tube out of a 14:12 sha and put it into a 15+ to get the progression of a 14:12 but the top end of a 15+. anyone got any input on that?

this is all very generic old-tech moby mods but i hope to get some huxpa out of em.

_RJ make sure you post results after running!_

Definitely will do.

I'm still on the fence if I should go for a high-dollar new Dellorto 15:15 or just opt for a cheapo 14:12 and possibly bore it to a 14:14... possibly.

Suggestions?

Seriously? I thought the 15:15 was like "the standard" when upgrading to an SHA?

Well that potentially changes everything...

ok well thats that then. id still like to try switching out emulsion tubes but even if that doesnt do me any good ill just run a 14:12 straight up.

On that same note I've ridden JesseS's stock (HEAVILY) ported moby with a 15 dellorto and the G3 exhaust that did a bit over 45mph for BBQ14, I guess he later fixed a few things with it and had it clocked at 50mph.

I pretty much hate SHA carbs on kitted or modded bikes on any occassion or setup. That motor that I was running finally lost all compression and was the saddest thing ever. My last trip on it was 100 miles long by myself when I moved from Louisville to Cincy and it used an entire tank of gas in about 45 miles. I'll rebuild it faster but it's going to be a minute.

The best carb for a moby is still the stock carb. Runs better than any SHA will ever ever. And you can still do over 40 on it. With all stock parts. And an airbox. Fact.

Hmm. I have a nice clean Gurtner here. I may take you up on this challenge and see if it runs better.

Jesse, since you know more about this than anyone else I know... I'm building my second 50V and I'm going to use the 12mm Gurtner AR2 from my first 50V on it (to replace the 10mm it had). Porting the cylinder to match the specs in the wiki (3mm up exhaust, 3mm down and wider intake, wider transfers, case matched) When it comes to adjusting the jetting am I going to have to solder and drill a spare jet, or are there other options?

I've not got a lot of experience with SHAs, but I put a 15:15 SHA on my first 50V and I don't like it... no low end at all and not much better top end. It's a basically stock bike with a 30mph cylinder and ported/smoothed bendy intake. Got a 14:12 in a box I'm going to replace it with to see if I like it better...

Thing with the small PHGB is you have to get the large intake for it, but really that's not a big deal, it's just hard to fit it under there, you can do it though.

Word Iain, haven't talked to you in a long time. I seriously put down the shit in a post on moby tuning about 3 weeks ago for porting a stock cylinder but I can't find the post. Owell, it's out there somewhere waiting to be found again, like treasure.

FWIW my Gurtner experiment was a total failure. Speed with Dellorto 14.12 - 31mph. Speed with Gurtner, 240cc jet, 25. I broke my Dellorto banjo in the process so now I am stuck with mediocrity...

dude ditch that stock intake and get a 15mm one from quarter kick or treats or someone.

And holy fuck. I've never seen anyone actually modify the cylinder head as recommended! That is sick! and cheating since you had a machinist do it ;)

The intake looks perfect, but there is a lot of work left to do for the exhaust.