Broken Mainshaft or Counter Shaft??? How bad is it?

[staysblazed]

Somehow the front sprocket fell off while riding. The main shaft that attatches to the sprocket has damaged teeth. I am assuming that I have to open the case to fix this problem. Should I do the whole bigger piston project just because the case has to be opened?? I use this 2001 400ex not to race, but to ride hard in trails and such. Right now the engine is simple and stock. I have full elka suspension and houser arm lonestar axle. etc. Engine...stock. How bad is my problem and what are my options?

[brokenmike]

when replacing the shaft you have to take the top end off anyways so go with a big bore kit,you might want to put a HD rod in it just for added insurance while you are there.It just depends if you can fork out the money all at once.

[staysblazed]

What is an HD rod?? How would replacing that give me more insurance?

[brokenmike]

An HD rod is short for heavy duty connecting rod.the stock rods tend to break on a stock bike and even more when you put a big bore kit on it.the HD rod will withstand alot more abuse.If the rod breaks you are looking at a HUGE repair bill.(cases,counter balancer,cylinder,gears,shift forks,shift drum. I have seen it happen) Hot rods have a whole crank shaft that you just drop it in an you are ready. How bad are the teeth on the shaft?they are supposed to be slightly tapered on the end.

[staysblazed]

The teeth are brockent off.....thats why I need to replace it. all of the tapered part is damaged. What is the cost of a HD rod?

[brokenmike]

the rod itself lists for 117.99 then you have to pay to get it installed into your crank halves.The whole drop in crank assembly lists for 273.99.the prices depend on your supplyer too. the counter shaft is 93.16 then you need a complete gasket and oil seal kit too.Do some shopping around and you might find some better prices

[Sjorge450R]

i just did this on my 300ex. Its a PITA, but if you have mechanical knowledge or know someone that can help its really not that bad. You have to tear open the entire motor, get to the tranny and replace the countershaft. The labor price for this is going to be nuts, just becaues of the amount of time it takes.

You will need a new piston/rings because you have to remove the head. You will need a complete engine gasket kit also. While its open, I would go and put a 426 kit on it IMO.

[staysblazed]

Hey what is the 426 Big Bore Kit?? I heard of the 425 and 440 kit. Where do I get the 426 kit??/