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Amal Vs Mikuni


sherpa t
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Im liking the sound of having a carb jetted and sent to you for under 90,

you think they will be able to help me with a carb for a

1983 MH 349 (its the montesa when honda bought it) the whole thing needs restoring.

It doesnt have the right carb, and instead of messing with ebay, buying a carb already jetted would be great.

is it just hitchcocks that do this?

Matt

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All of the usual dealers that cater for twinshocks will be able to supply you with a MK1 Amal for the Bultaco or a MK2 Amal for the Mont - I'm guessing that's what the Mont should have. Just that not all of them are likely to have one on the shelf.

If you have spec sheets in manuals then there is no problem with jetting for the standard type carbs as the spec sheet will list them. The problem comes when fitting a Mikuni, Dellorto or other as there is no spec sheet so it is trial and error or using someone else's settings as a start point.

The places most likely to have the MK1 and MK2 Amals in stock are Millers, Bultaco UK, Surrey Cycles or Hitchcocks. Miller and Bultaco UK (for the Bult only) should know the jetting, the other two probably won't so that is where your spec sheet comes in handy.

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Forgot to mention also that if you go for a Mikuni the diameter of the intake on the back of the carb may be a different size from the Amal, therefore you may have to improvise for the intake rubber/hose from airbox to carb.

As regards performance advantage with the Mikuni, personally I don't know. Some say throttle response is better/cleaner with a Mikuni, although the Beta owners seem to hate them. All I can say is that when I had my original Ossa MAR back in the 70s it ran perfectly on it's original MK1 Amal - wish I still had that bike..... When I had a reed valve fitted to my current MAR, I was still using an Amal MK1 and had no performance issues at all. Can't say I've ever found they go out of tune as there is only a pilot screw to adjust. Had a new Mikuni on it in later years and couldn't really tell any difference - other than the constant flooding when the bike was parked up or leant over. Then again, I have another MK1 Ossa which has an older Mikuni from a Suzuki fitted and that runs clean as a whistle right through the rev range - but Mick Andrews set that up.

If you do go for a new Mikuni Allens is the best source for that as someone there runs a Bult with a Mikuni on so should have the jet sizes needed. Also, make sure they supply the carb with the rubber tipped float needle and housing to match as it should stop the flooding - did on mine anyway. Why they don't come as standard I don't know...

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Forgot to mention also that if you go for a Mikuni the diameter of the intake on the back of the carb may be a different size from the Amal, therefore you may have to improvise for the intake rubber/hose from airbox to carb.

As regards performance advantage with the Mikuni, personally I don't know. Some say throttle response is better/cleaner with a Mikuni, although the Beta owners seem to hate them. All I can say is that when I had my original Ossa MAR back in the 70s it ran perfectly on it's original MK1 Amal - wish I still had that bike..... When I had a reed valve fitted to my current MAR, I was still using an Amal MK1 and had no performance issues at all. Can't say I've ever found they go out of tune as there is only a pilot screw to adjust. Had a new Mikuni on it in later years and couldn't really tell any difference - other than the constant flooding when the bike was parked up or leant over. Then again, I have another MK1 Ossa which has an older Mikuni from a Suzuki fitted and that runs clean as a whistle right through the rev range - but Mick Andrews set that up.

If you do go for a new Mikuni Allens is the best source for that as someone there runs a Bult with a Mikuni on so should have the jet sizes needed. Also, make sure they supply the carb with the rubber tipped float needle and housing to match as it should stop the flooding - did on mine anyway. Why they don't come as standard I don't know...

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Well here goes! After talking with Lynn Mobley, and the info in this forum, I am going to mount a Mikuni. I have the resources (machine shop) to build the adapters necessary to make it fit. Lynn says a 25mm is the trick setup. Bultaco calls for a 27mm but Lynn says the 25mm gives better throttle response off idle. I realize Senior Bulto would frown on this conversion but I don't need anymore fives account the bike died.

Now my next question - what can I blame any future fives on? Should have the bike running by the middle of next week - will keep you all posted.

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