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Post by Reign on Mar 19, 2010 16:15:58 GMT -5
Wow, that's amazing. Looks like everything is working out for you ;D I'm actually thinking about taking a look at the 40FM now that I know a BBK would bump up the power even more.
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Post by drawkward on Mar 20, 2010 19:21:49 GMT -5
From the base (where the base gasket sits) to the top (where the head gasket sits) is almost exactly 68.5mm Probably closer to 68 though. Again, I'm really sorry about that. At least you're figuring out a way to make it work. Hope it all goes well for you in the long run. I guess 40FM's arent the optimal choice for BBK. Wow I can't believe I didn't notice this, but his is 3 mm off from what your measurements are. Did you use a digital caliper? Could your measurements be off at all? |
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Post by Reign on Mar 20, 2010 22:02:34 GMT -5
From the base (where the base gasket sits) to the top (where the head gasket sits) is almost exactly 68.5mm Probably closer to 68 though. Again, I'm really sorry about that. At least you're figuring out a way to make it work. Hope it all goes well for you in the long run. I guess 40FM's arent the optimal choice for BBK. Wow I can't believe I didn't notice this, but his is 3 mm off from what your measurements are. Did you use a digital caliper? Could your measurements be off at all? I don't own a digital caliper, only analog. I just did a quick measurement with my mini tape measure. |
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Post by drawkward on Mar 20, 2010 23:04:24 GMT -5
Well, he seems to know a lot about them, hopefully it's not a loss. I'll let you guys know, obviously.
Oh and btw, I picked this up from HF tools. $1.99, I think it was on sale. Couldn't pass it up. Should get one if you got a HF tools around. Completely accurate according to the BBK I got - Read exactly 10mm on the pin, and exactly 64mm on the cylinder.  |
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Post by drawkward on Mar 26, 2010 19:05:05 GMT -5
Got the FREE replacement kit Carlos sent to me today. Was pretty nervous when I was about to put it on and test fit it. Here are the results. (And yes, these are just about the best pictures I can get...)  BDC - All ports are completely exposed. About 2mm from piston walls to the lowest ports.
TDC with no base gasket just BARELY shows the crown of the piston over the cylinder top. I'm talking like .5mm here, if that.
Just a fun comparison.I wish I could get on her right now and test out the kit. Damn variator! Oh well. This gives me an opportunity to make sure I do it right, as well as giving me the time to go ahead and polish the exhaust port. |
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Post by 90GTVert on Mar 26, 2010 20:05:11 GMT -5
Glad you finally got a kit that will work. Kinda sucks that it's just in time for your vari to give you a hard time. I must be seeing something wrong or that TDC pic isn't actually TDC. You said the crown is .5mm above the deck, but it looks a couple mm below deck there.
While you're looking for stuff to do, if you haven't already, check the piston ring end gap. It should be roughly 0.11mm per inch of bore. 48mm / 25.4 = 1.89" bore. 1.89 x 0.11 = 0.21mm or 0.008". Put the piston ring in the cylinder and use the piston to make sure it's straight. Check the end gap with a feeler gauge and file it gently with a fine file if the gap is too tight. Don't forget to chamfer those port edges too if necessary.
I saw that you noted a 41mm stroke in the port map thread. It sucks that parts are harder to find but that's a nice stroke of luck ;D since you got a BBK now. A standard 39.2mm stroke would make 71cc with a 48mm kit. Your 41mm stroke ups it to 74cc. The stroker motor I'm putting all this effort into is less than 1cc larger than what you have here.
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Post by drawkward on Mar 28, 2010 17:47:16 GMT -5
I checked the gap. Wasn't even close to being right. Filed it down as much as I felt comfortable doing, but it still isn't wide enough for me to fit my keychain feeler gauge in (.20mm). On a side note... I went to go clean and jet my carb while I still can. The jets aren't even close to fitting! lol... I should have listened to 2strokd from the beginning (he was right about my jets being the Mikuni VM11/22 series). I wish I had this caliper a few weeks ago! I will never be without one again, that's for sure. This has been a pretty time and money consuming venture without using a caliper to guide me. ALL of this could have been avoided if I would have taken the time to just measure, and remeasure, everything before purchasing. Oh well, you live and you learn. Pic of jet's below. The one on the left is the stock, the right is one of the 11 new ones I have that don't fit.  Oh and if anyone has a Dellorto carb that needs a jet kit at a really really cheap price (not trying to make my money back, just don't need them) - I'm your man! ...Unless I just buy a new carb to match the jets!  |
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Post by 90GTVert on Mar 28, 2010 20:24:05 GMT -5
Dellortos are 6mm x .75 and Mikuni is 6mm x .8. Those should be interchangeable. Look at my pics of 6mm DellOrto jets with the stock jets... 49ccscoot.proboards.com/index.cgi?board=carb&action=display&thread=364Have you taken a caliper to the threads of the stock jet or verified that what you bought are actually 6mm and not 5mm? EDIT : Sorry, my initial post was a little off. I was speaking to a comcast rep at the same time. |
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Post by drawkward on Mar 28, 2010 21:41:46 GMT -5
All good, just had me confused for a second  Have you taken a caliper to the threads of the stock jet or verified that what you bought are actually 6mm and not 5mm? The stock threads read just about 6 mm. The "Dellorto" jets I got read at exactly 5 mm. I can slide the new jets right into the stock jet's threads very easily, without threading. There is a quite noticeable difference in the size. The blurry picture really does not do it justice. My stock jet is HUGE compared to the "Dellorto" jet. I'm going to pop him (treatshq) an email and see what he can do regarding returns. I've been really cool with him, and he's been really helpful back, so hopefully he can help me out. |
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Post by 90GTVert on Mar 28, 2010 22:23:34 GMT -5
As you just found out, Dellorto makes 5mm and 6mm jets (prob more too). Sounds like you ordered the 5mm. Good luck with the return.
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tate
Scoot Junior
Posts: 9
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Post by tate on May 31, 2011 18:32:53 GMT -5
So basically long story short the FM engine is the best scooter engine ever?
Man I am kicking myself. I JUST sold a Eurostrada RX8 with philips heads on the variator cover. Dammit.
Oh well, pretty sure my Sundiro Akita has one and pretty sure I am going to buy a Linhai Powermax that has one also.
If I read this correctly thw 40FM is a minarelli with the crank from a Jog 90 or Rattler 110 engine?
So could we in theory just go ahead and take a cylinder from a Jog 90 or Rattler 110 and slap here on there and end up with 100cc or so?
Or is the cylinder skirt too fat on a 100cc cylinder? Could one bore out the case mouth? I have done that plenty and its real easy.
I am real pumped. My Akita always hauled a lot of ass but I never understood how it could be that much faster than other Jog wannabes. Now I know its because it is closer to 65cc.
Tomorrow I get a Linhai PowerMax that has all the light weightness of my Akita PLUS a front disc brake.
This buid is going to be epic.
I have been squeezeing every little ounce of power out of ancient mopeds for so long that now when I work on scooters and performance gains are so easy I feel like I am getting my speed real easy and cheap.
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