big bore 200x info wanted

[85200xer]

I have a 85 200x, I am putting a powroll big bore piston kit on it the 12.5 to 1 comp on it with a race cam. I have a supertrapp exhaust on it and was wondering what size of carb I should run on it? (stock?). also what type of port work to be done. head shave? stroker crank? straight race fuel or race/premium mix? twisted appreciate all that reply

[85200xer]

nobody knows anything about this? (

[Da_Catt]

Try a 28mm carb, that is what most people run. when you say race cam what are the specs? If it is a race cam then you will have power in the high rpm's only. the hi compression piston will make up for some of the low end. If you are reving the engine hi like you would with a race cam, then do not stroke it. the stroke kit shortens the rod and will cause a high piston speed. not good. do not shave the head it will mess up your cam timing and you could have piston to valve problems. besides 12: compression is enough. with 12:1 piston powroll says to run a 1/2 race gas and 1/2 premium. port work can be done if you want, no harm if done right.

[85200xer]

lift on cam= in-.395'' ex-.395''

should I worry about the rod bearings or the crank snapping?


thanks for the info

i have a x running 12to1 .toure cam. dg ex.k and n fillter.carb wsa the most work.stock carb jet from 108 stock to 142.don blew crank once.top in was shot.put a new one. last about 30 houres apice.is not worth it and big bore kits or good but once you cut your case to fit you cant go back.put you a 10 to 1 piston small cam and a k and n fillter. jet to fit and ride

Hey 85200Xr, I also have an old 85 200X and have run lots of different things...The carb on my bike is a Mikuni 28mm Flatslide that came in kit form many years ago with an intake manifold included. The main problem with this carb is frame clearance. I had to heat and dimple the frame tube to make clearance for the carb (A common mod back in the mid 80's). If you are going to retain the airbox you will also have to cut/bore/scrape some rubber from the inside diameter on the airbox connector tube to be able to fit over the carb intake bell. In the end it worked out pretty well but not an easy "Bolt On" mod. I know that the modern 4 strokes are running much bigger carbs than in the 1980's so maybe something different is available now.

I have also run different compression pistons and should recommend the 10.25-1 over the 12-1. The 12-1 almost requires race gas and will detonate/ping on straight 93 octane. With the cylinder bore job you do not need to bore the cases. Wiseco offers up to 2mm oversize pistons with 4 steps over in 10.25-1 and 3 steps over at 12-1. I dont know where guest is coming from with his comment on boring the cases unless he is talking about resleeving the cylinder with a larger diameter sleeve that would requre a custom piston and case boring etc...I dont think he quite knows what he is saying there. As far as the bottom end goes (Crank, Rod, etc) they have been bulletproof as long as yours is in good shape. I have had a failure with a custom Falicon "triangle" crank but that is another story. If you are running a stock bottom end you will not have any problems. Strokers have more of a chance to come apart as most run a shortened rod but ask Powroll and see. They have the experience. They will also advise on the porting. Dont mess with shaving the head, The piston will be plenty. Good luck.

Curtis

[Curtis-Tecate3]

Whoa, The above post was mine. I guess I didnt sign on or something...???

Curtis