I know its been a while, but I thought I'd update on my progress...

I put the 500HO cam in it like I said I was going to, and replaced the exhaust rocker. I also put the 42mm Predator carburetor on it using a Sportsman's 40mm carb boot. It is a bit of a tight squeeze, but it worked easily enough without having to modify it or lubricate the opening.

I just got in two new idle jets, because its currently working at below one whole turn out on the idle fuel screw. It currently doesn't like to idle very well when its warmed up, but starts back up no problem. So one of these two smaller jets will get it to idle perfectly I'm sure.

I've gotten it up to 40mph so far as it currently sits... But I know it has more, because I've had it faster with the smaller carb, and stock cam. The bigger carb has a 170 main jet in it, which I would assume would be to big, since it came off of a 500 HO engine. So I went ahead and ordered a 175 and a 165 jet so I could compare the difference of going each direction on the main jet. Unfortunately they must have been out of the 165, because it didn't come in with the rest of them, and wasn't listed as being sent on the PO. I can only assume it will come within the next week.

I also went cheap on the air box and modified the orriginal... I cut about half the rubber tube off and stuffed a 2" 45 degree black PVC pipe (male on one end, female on the other) into that. From there I used a 2" no-hub coupling to connect the female end of the pipe to the carb, which ends up being nearly identical in size. This makes the coupling have to be stretched a little bit when putting it on, of course. But, the rubber piece which pipes are meant to butt up against inside the coupling also prevents the PVC and carb from rubbing against each other.

So far it has been a somewhat costly yet fun project. I've been cleaning it up and painting parts of it to look a little nicer here lately while waiting on the fine tuning parts to come in... Hopefully I'll have it purring like a kitten no matter the temp and hitting top speed here soon.

 

What elevation are you at? I put a 152.5 main in mine, I live at 5200 ft elevation. !65-170 seems a little high to me.

 

It seemed *really* high to me too. I'm at around 1k ft. I got a 155 initially, but accidentally got the wrong series of jet. It ran like crap with it in of course... I was thinking that the numbers across different series might have been equivalents but as soon as I took the wrong one out, I realized that was a stupid theory. When I changed them out yesterday I noticed the 155 was about the same size orifice as the 170 I originally took out of it, but the nozzle is designed differently.

I really wish the 165 had came in instead of the 175, because it seems to run the same as with the 170... which is way too rich. Even if it was too big, the 165 would have given it an improvement I'm sure.

Anyone have a good guess as to what I should probably be using? Its still the stock 425 Motor, but with a HO cam, and a 42mm Carb. I'm thinking a 155 in the correct jet type might be the better guess.

 

I would think a 152.5 or 150 would be enough, is there a shop with all the different sizes aroun, I have alot of the mikuni large round, the only way to know is to try them , some shops will trade jets, others make you buy them, The predator carb should have the mikuni large round jets, take the one out of your old carb and try it, it should be a 145.

 

The 155 I initially ordered was a larger diameter than the one I took off of the Predator carb, and the same diameter as the 140 main that is currently in the original carb. Not sure if someone might have swapped it out before with an incorrect jet type, or if they're supposed to be the smaller type. But, it runs better with a 170 of the smaller type than the 155 of the larger.

I haven't checked for jets at my local shop, because everything I have ever gone there to ask them about they would have had to order. And last time I ordered something from them it took almost two weeks to get there. This might however be an exception, because so many others use Mikuni carbs too. Might as well try though... worst thing they could say is it has to be ordered, and would cost way to much. To which I say, never mind... lol