350 Power Valve in a Honda ATC 250R question

[arlaunch]

I am tracking a CT 350 Power valve cylinder on the list in my local area.

Do any of you fine fellows have any information if one of these things would fit in an ATC 250R?

I would be running the long rod/spacer plate set up.

Not sure why i am exited about this....???

But it sounds cool!

[yaegerb]

If by "fit" you mean bolt on the cases, yes. But there is more to it than that. You will need to run a long rod (as you stated) but that also means you need to get your cases machined or "trenched" so the crank will work. If you get the proper rod/piston, you shouldn't need to use a spacer.

I also enjoy power valves, as it makes a smoother/more predictable power band and allows you to lug around in lower gears. Remember that it is another wear item. For those to work correctly the must be cleaned periodically to ensure proper function.

[The_Steve_Man]

It will fit. With the long rod and spacer, you can't use your top mount. That is not a big deal. You will need to get your cases machined to fit the bigger sleeve. It is not a simple bolt on.

There are a couple guys on here that have big bores that may chime in.

[arlaunch]

Cool fellas!

Thanks!

I just wasn't sure if the actual whole motor would fit back in the frame of an ATC with one of these behemoths bolted on. It is hard enough changing a spark plug with the little 250.

I am somewhat familiar with the internal stuff due to way to many burned hours reading about this interesting stuff.

[RIDE-RED 250r]

The above posts are correct about having your cases bored for the larger sleeve protrusion into the cases.

With the spacer you will have little to no clearance for your OEM spark plug cap, particularly if your trike is an '85. This is mainly due to the fact that most, if not all aftermarket heads, including big bore heads do not have the angled spark plug hole like the OEM head. With the TRX this is largely a non-issue, but it poses a problem with the trike frame..Thankfully it is relatively easy to remedy, I ran into this issue with my short rod 350 kit (no spacer) and I ended up using a small weedeater spark plug cap. Remarkably, I have had zero issues with it. Others have suggested using "shorty" sparkplugs. This is also a viable solution, but they are more spendy than the standard b9es and less readily available at local parts/hardware stores.

[arlaunch]

Thanks RR

So,

Do you think with your set up would work with the 4mm spacer plate?

I happen to only have 85 R's

This is sounding a little tough?

[RIDE-RED 250r]

As I stated above, there is a solution and its pretty simple and effective
Using a small chainsaw of weedeater sized spark plug cap will leave you plenty of room, and I would say that even using the 4mm spacer you will be fine as well. Idk if you still have the OEM cap on yours or not, but they are quite bulky and won't play well with a head that has a straight spark plug hole.

If you want the CT 350 kit, go for it! Then send your cases to ESR or any of the other reputable builders to be bored. It will be cheaper if you tear down to bare cases yourself.

Not tough at all! :beer

I don't mean to pile on and "spend your money" but I would recommend a bottom end refresh while doing your big bore. It's going to make alot more power than stock, and you want to be sure your bottom end is up to the task. CB bearing replacement would be a smart move as well if they have not been replaced.

[christph]

Regarding spark plug clearance, LA Sleeve--the people that provide CT with cylinders--makes a dome where the spark plug comes out at an angle. If you look closely at the image you can see it.

https://www.lasleeve.com/big-bore/l.a.-sleeve-big-bore-kit-niks307