jet?? stock ported moby 15/15 Sha Dellorto

mikeACR512 /

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Jan 25, 2009 03:12AM

So I opened up the the exhaust and intake ports on a 25mph moby. I am not running a base gasket but I do have a head gasket on. My plug looks a bit rich and the bike is only hitting about 28mph. I set the timing by pulling the cam and using a dial indicator to find 1.8mm B.T.D.C I then hooked up a static timing light and rotated the cam CLOCKWISE and just as the light started to turn on I placed the cam. When the points were opened I used a feeler gauge to gap them at 3.5 so unless I am confused about the timing it should be set. The bike boggs out a bit and dosnt seem to have the peppy pull that my old 35mph stock bike had.

<p>My question is would running a slightly off jet cause the bogging out feel? (I have a 60 in)

<p>When setting the timing do you want your cam to be placed by rotating the cam clockwise or counter??

Re: jet?? stock ported moby 15/15 Sha Dellorto

Andy /

akpasta

Jan 25, 2009 04:31AM

I just had my cylinder ported at 1977; you'll need to do some tuning afterward.

When you make ports larger on a cylinder, you lose a little compression, and thus, some balls. It's much more apparent on a 50cc cylinder. The symptom will be a bit of bogging on the low end with stock SHA filter. I was running a 61 jet, now I'm running a 68 with no air filter, that's the first thing I did to get it to not bog.

First, get a high flow air filter (which is better than NO air filter... for reasons I don't quite understand but are explained if you search 'air filter' in the wiki)... also check out the SHA filter mod in the wiki. Then mess with jetting. You can bog from being too rich and you can bog from being too lean. They're slightly different, but I haven't figured out exactly how.

Also, you should lighten your variator, which will cause your clutch to grab at higher rpm and give you more acceleration off the line.

I just re-assembled my engine after having it ported and I would caution against running without a base gasket. Only reason is, when I was looking at the engine off the bike, it didn't look like the case and base of the cylinder were meeting exactly, and you never can be too careful. I cut up an old LP jacket and used that, works great.

Elliot told me to leave my timing the way it was.... mild porting you shouldn't have to mess with timing.

Re: jet?? stock ported moby 15/15 Sha Dellorto

Emperor Swagustus /

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julian

Jan 25, 2009 11:05AM

I ported a 25mph stock cylinder on my le moped and found that with the stock dellorto air filter in place, a 58 jet was about perfect. Also, I would encourage you to use some sort of head gasket, even if it is just a beer can. I decked my head and also matched the cylinder, so they were very flat and smooth, but still had leaks. Hondabond works well. Another thing you can do is take the stock motobecane head gasket and peel it apart. It is actually made of a bunch of thin aluminum sheets which come apart pretty easily and one or two of those individual sheets make a good thin head gasket.

Yes, a slihtly wrong jetting can make your bike ride differently, although I do not think a 60 instead of a 58 will limit you to 28mph. Something else is up I think; check to make sure the head is sealing, as this will kill your compression and could really foul your plug, even on a healthy jetting, due to incomplete combustion. I assume you ported according to the wiki?

You want your timing to be set by rotating the cam in the direction the engine normally runs during operation.

Re: jet?? stock ported moby 15/15 Sha Dellorto

mikeACR512 /

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miketorres OP

Jan 25, 2009 11:22AM

I have a massive air leak at the base. I went out started it up and sprayed the motor with some carb cleaner and it shut down in a sec. Fuck I dont have a base gasket

Re: jet?? stock ported moby 15/15 Sha Dellorto

steve /

stevep1989

Jan 25, 2009 06:24PM

maybe im missing something but why would you not have a base gasket in the first place? luckily you can cut one out of gasket paper so get to it. get a base gasket in there, reset your timing (the base gasket will make a difference), choose whether or not you want a head gasket (up to you, could help regain some low end balls) and start retuning from there.

Re: jet?? stock ported moby 15/15 Sha Dellorto

Mick Baltards /

aircooled17

Jan 25, 2009 08:19PM

Handy's has base gaskets in stock, individually.

Re: jet?? stock ported moby 15/15 Sha Dellorto

finny /

Jan 25, 2009 10:05PM

You can make out of gasket paper in not time. Head over to your local true value hardware shop and find the thinnest gasket fiber paper they have. You NEED to run a base gasket!

Re: jet?? stock ported moby 15/15 Sha Dellorto

Chris Rice /

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chrisr

Jan 26, 2009 12:20AM

Air filter is good because with no filter you will get dirt or debris in your carb. It's like having sex without a condom. It might feel better, but there is a good chance it will fuck you up in some way or another...

Re: jet?? stock ported moby 15/15 Sha Dellorto

mikeACR512 /

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miketorres OP

Jan 26, 2009 03:16AM

I made a paper gasket leak is gone. it was still running kinda shitty so pulled the $40 piers pike I got from treats and slapped on the stock pipe and boom it was flying WTF?? I have the same bike on my other stock moby and its great???

Re: jet?? stock ported moby 15/15 Sha Dellorto

steve /

stevep1989

Jan 26, 2009 11:46AM

what did you just say?

Re: jet?? stock ported moby 15/15 Sha Dellorto

jaym /

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jaym

Jan 26, 2009 12:39PM

wow

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