Topic: Keihen (sp?) vs Mikuni vs stock ?

[Uncle Ernie]

I'm thinking a lot about carbs for my '75 400. Some folks say I should rebuild the ones I have (only using stock Honda parts instead of aftermarket), some say Keihen flat sides, and some say Mikuni. Any thoughts?

[Jonesy]

Are you trying to soop it up or are you happy with it as-is? If you like it the way it is you should be fine rebuilding the carbs you have, provided they are not worn out or anything like that. And yes, rebuild using genuine Honda parts. Many have had issues with the aftermarket parts (particularly needle jets) being a different size and screwing up the running quality of the engine.

My 2 cents...

[Tim2005]

Is the engine tuned at all? If not, I'd stick with the stock carbs (rebuilt with genuine Honda parts) & spend the $s on a 460 kit & new camchain. I'm in the middle of sorting out Keihin CR flatslides on my 460/4 & it is quite a bit of work/cost, and that's before I start with working out the jetting (if anyone's reading this & has experience of this conversion I'd appreciate any jetting info).

[Uncle Ernie]

Well, we DID use aftermarket junk and now I think something is hanging up. I lose a cylinder after it warms up about 20-25 miles. I'm not trying to soup it up, but that 460 kit does sound interesting... but it does real good when I keep the revs up. When I'm riding in a spirited manner, I keep it between 55 and 65K.

[eldar]

when you lose the cyl, what does the plug look like? Is it really sooty? It may be possible that there is just an adjustment that is off.

[Uncle Ernie]

I haven't taken the plugs out yet. I have to do it when it happens and then it's (as we say here) hoteehell. When I wait for it to cool down it starts again. I need to ride to a friends, hang out, and THEN take the plugs out.   Should happen soon- I'll ride to work and take them out at lunch.