E: Engine Comet Mongrel
- Thread starter Cyborg
- Start date
Also looked at the round slide Mikuni/UFO set up but for the tiny cost thought the semi flatslide Keihins' were worth a try. Have tended not to use the larger sizes of Mikunis' on twins as I think they have a fairly broad floatbowl which complicates the clearance of the front carb and the rear pot. The Keihins' seem to be fitted to a lot of MX 2 strokes but the bigger sizes also appear on big single 4stroke KTMs etc. You may get there before me !.
Hi, The UFO is a pre -made "spacer" kit
Sorry site went into maintainance mode as i was replying, the UFO is a USA made kit which makes the round slide Mikuni behave very like a smoothbore carb, read the reviews online, could be an inexpensive and worthwhile mod.
here's some info on the UFO. USA and UK.
http://www.motocarb.com/ufo-insert.html
http://thunderproducts.com/product/u-f-o-ultimate-flow-optimizer/
Yes the brakes are CBX 550. Some folks turn their nose up at them and say they are hard to work on, but I happen to like them and quit frankly don't understand why someone would make a fuss about having to remove the wheel and a few items when changing pads. One writer complained of brake fade, but with OEM pads and clean brake fluid, it's pretty hard to beat them into submission.
Cast iron ventilated rotors and duel piston callipers.
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I'm wondering wether this mod could be done on Amal mono block slides
Mac
Cyborg, On my similar Comet project I will be using the same ignition system and a 36mm Mikuni with UFO as recommended and set up by Steve at Motocarb. I was going to go smaller but Terry Prince recommends a 38mm for his top end and Steve seemed to think a 36 would be a good choice. Here is a picture of the UFO, and as you can see it required a bit of machining on the slide and apparently in the bore, but I could not tell where that was done. Motocarb set it up for the changes with jetting, but included some extra sizes so it can be fine tuned when I eventually get it on the road. I bought the large intake bell they offer, but may or may not use it and fit a filter instead. I may make some sort of screen for it to keep out the sparrows.
I don't see why not.
Something similar could likely be made for most slide carbs to simulate some of the characteristics of a real smoothbore carb. Could be worth reading the reviews and installation instructions for the UFO kit since the manufacturers say much smaller air jets are needed to correct the mixture. Personally I would be tempted not to experiment unless you already have a good spare set of monoblocks on hand, the other option is leave the Amals alone as spares and buy a set of Mikunis (£70. each on ebay) and a UFO kit to suit.
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Finally dealing with the 1/2 time pinion after a multitude of excuses. After doing some measuring, it appears that I will need at least a +8 if not a +10. Hopefully nothing larger. When the pinions arrive and it turns out that I need more than +10, (I see that there isn't an oversize large idler available) I'm assuming I will have to use an oversize 1/2 time pinion on the breather assembly which will allow me to move the large idler down.
I'm using an Alton, so not dealing with the seal. One thing I did notice is with the Alton, it would likely cause the large idler to ring at low speed if there was any extra backlash. Just turning the gears by hand, the push/pull of the magnets would cause the large idler to ring quite loudly. Perhaps that won't be a concern at idle speed, I don't know. Maybe it will be drowned out by the rest of the racket?
I'm using an Alton, so not dealing with the seal. One thing I did notice is with the Alton, it would likely cause the large idler to ring at low speed if there was any extra backlash. Just turning the gears by hand, the push/pull of the magnets would cause the large idler to ring quite loudly. Perhaps that won't be a concern at idle speed, I don't know. Maybe it will be drowned out by the rest of the racket?
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A few thoughts:
The breather 1/2 time pinion can be ANY size as long as it engages with the the large idler and does not jamb on it - no issues with 'excessive' backlash causing noise as there is no load - err should be no load - on the breather assembly when its rotating. Remember to widen the slit in the breather sleeve to get a substantial improvement in breather effectiveness - more into in 'Tuning For Speed".
Using an Alton in a Comet - do yourself a MASSIVE favour and read the attached from OVR 50 - silicon sealant can be a motors worst enemy. I now have over 2,000 miles on this seal with the Alton in my Comet - First time EVER I have NOT had oil over the back of the motor and gearbox in over 60,000 miles of use.
As to noise from the Alton gear - its a plastic gear and once the motor is running it does not have the opportunity to rattle about so no contribution to any 'ringing of the large idler. Ergo backlash is not a big issue here when the motor is running. Plus the Alton shaft MUST be in the centre of the seal.
The breather 1/2 time pinion can be ANY size as long as it engages with the the large idler and does not jamb on it - no issues with 'excessive' backlash causing noise as there is no load - err should be no load - on the breather assembly when its rotating. Remember to widen the slit in the breather sleeve to get a substantial improvement in breather effectiveness - more into in 'Tuning For Speed".
Using an Alton in a Comet - do yourself a MASSIVE favour and read the attached from OVR 50 - silicon sealant can be a motors worst enemy. I now have over 2,000 miles on this seal with the Alton in my Comet - First time EVER I have NOT had oil over the back of the motor and gearbox in over 60,000 miles of use.
As to noise from the Alton gear - its a plastic gear and once the motor is running it does not have the opportunity to rattle about so no contribution to any 'ringing of the large idler. Ergo backlash is not a big issue here when the motor is running. Plus the Alton shaft MUST be in the centre of the seal.