Carby dual carburetors, one gas, one e85, suggestions?

[jatgm1]

i replaced the cork gasket in my carb so it wouldnt get eaten away(made one from some autozone stuff that seemed good) thinking i could either use something like this

http://www.ebay.com/itm/30-mm-Dual-...169451?hash=item3abd30686b:g:oMcAAOSwuAVW1Eqz

with two carbs , and two tanks, or add a splitter and second fuel cutoff switch to another gas tank, but then i would need to screw with the carb every time i switched from one to the other. suggestions? and with all due respect, everything can be done, so telling me otherwise will just make sifting through posts more difficult, thank you very much!

 

[45u]

My opinion do not wast your money just put a bigger better carburetor. Have you ever sink two carburetors? I do it all the time as I work on motorcycle as a living and now that I am retired I am still working on them as many will not take their bike anywhere else.

 

[butre]

syncing carburetors is a huge pain in the ass and not even a little bit worth the effort on a single cylinder engine. just get a mikuni VM18 and a manifold that fits. it won't save you money but it will save you a whole heap of headache and 2 or 3 weekends of trying to get that junk tuned right.


that 30mm thing is false advertising anyway, the area is only equivalent to a 20mm carb. they got 30mm by adding the diameters, not the area, and the vm18 has better flow characteristics and an idle circuit to make up for that 2mm

you would also have to have airtight blocker plates in both plenums if you were to run one for one fuel and one for another. it's easier to just have a carb with seals for e85 and swap jets if you're changing fuel types.

I also presume you didn't change out the main seals to cope with the e85 either.
e85 is useless as a fuel in anything without forced induction anyway, the dynamic compression ratio even with the smallest chamber aftermarket head of 5.3cc is only about 9:1 or so depending on your primary compression ratio and port timing

don't bother with e85 until your dynamic compression is 16:1 or greater

 

[45u]

syncing carburetors is a huge pain in the ass and not even a little bit worth the effort on a single cylinder engine. just get a mikuni VM18 and a manifold that fits. it won't save you money but it will save you a whole heap of headache and 2 or 3 weekends of trying to get that junk tuned right.


that 30mm thing is false advertising anyway, the area is only equivalent to a 20mm carb. they got 30mm by adding the diameters, not the area, and the vm18 has better flow characteristics and an idle circuit to make up for that 2mm

you would also have to have airtight blocker plates in both plenums if you were to run one for one fuel and one for another. it's easier to just have a carb with seals for e85 and swap jets if you're changing fuel types.

I also presume you didn't change out the main seals to cope with the e85 either.
e85 is useless as a fuel in anything without forced induction anyway, the dynamic compression ratio even with the smallest chamber aftermarket head of 5.3cc is only about 9:1 or so depending on your primary compression ratio and port timing

don't bother with e85 until your dynamic compression is 16:1 or greater

I agree I would never run e85 in mine. Everything I have read says 91 octane or more. As far as setting twin carbs not a big deal to me as I have been sinking carbs on old British bikes for years but not on a single cylinder as they only run one as one is more then enough. The dual carb for these bike are more for show and not riding. Stock compression is 6 to 1. The stock wrist pin bearing will not handle much over 7 to 1 and many mess up at stock 6 to 1. The Chines know the quality so they do not have a very high compression or rpm.

About all these engines stock will turn is 6K rpm which most 2 cycles turn 10K or better other then yard equipment.

 

[butre]

stock static is 6:1, stock dynamic after factoring in crankcase compression is probably 5:1 at best. my engine runs a static of 14.4:1 and dynamic of 13.5:1 after factoring in crankcase compression. all made possible with the help of a bronze bushing instead of a bearing. upgraded studs probably helps too

even in my engine, the 105 octane rating of e85 is unnecessary, I get by just fine on 100 octane avgas, and make more power doing it because ethanol has about 33% less energy per gallon than gasoline.

 

[45u]

So the bushing holds up fine? The reason I ask is I was told on two cycles they will not hold up running a bushing and is why they use a bearing. In all my 40 plus year of working on motorcycles most of the time for a living I have never seen a bushing in a two stroke. I have seen the bushings for sale but not sure about them. How many RPM s do you turn? Mine runs fine on pump perineum.

 

[butre]

holds up fine, but you can't run plain bronze, you gotta run oilite. old 2 strokes, older than either of us, that didn't spin very fast would run plain bronze bushings without problems, but 2 stroke technology advanced quicker than bushing technology and the switch to roller bearings was made. now days the use of roller bearings is mostly down to hard-headedness.

it's also very necessary with a titanium wrist pin, the hardened steel bearings chew through titanium like it's nothing.

they don't last as long as needle bearings but the failure mode isn't catastrophic and it shows signs of impending doom a couple dozen miles in advance which gives ample time to go ahead and replace it before it does fail.

my engine tops out at 11500 rpm but being as that's cresting 60 miles per hour it rarely hits that.

 

[butre]

there was one online store selling aluminum bushings for these engines. now that there was ill advised.

 

[45u]

I have worked on quite a few of OLD 2 cycle motors talking 40 and 50s and none of them revved very high. What held back 2 cycles for years what leaning about the exhausts system and when the got that right things changed quick. Would love to see a video of yours turning 11 grand. You must rebuild yours often. Might just have to make a rode trip to see this beast.
Thanks
Jeff

 

[45u]

there was one online store selling aluminum bushings for these engines. now that there was ill advised.

See a seller on eBay that sells brass or bronze ones. When I post a link I do not make anything and is not mine I am just trying to help others with pictures.