exhaust valve cover spacer??

[ekim221]

ive just noticed the 96 cr250 i just bought has a spacer on the e.v. cover. its about a half inch or so. i knew the bike ran really well, pretty good low end, great response, and so on. so i started wondering if it had been ported or something. thats when i noticed it had this spacer. what might this thing do to the bike? what ever it is it dosn,t seem to hurt.
thanks[IMG]F:\DCIM\100KZ710[/IMG]

[ossagp1]

That particular cylinder was probably about the best balanced one that HONDA ever sent. It is the model that Yamaha started off with when they copied the bore and stroke. The cover spacer as you say doesn't hurt it. If you take the cover off and shine a flashlight into the exhaust port you will see what is going on. The subexhaust port when closed, opens up into that chamber provided and increases the volume and suposedly provides some benefits of a longer header. It doesnt seem like it would to me, but that was one of the explanations I got from the people who sell the spacers. Some of what it does runs counter to how you would think it should work in making better low end, but it seems to. We used to stack gaskets to make that change, then made spacers. It has been done since at least 92.

[ekim221]

ok i see. my bottom end sure isnt lacking but i wouldnt say its the most impressive ive ridden either. i guees when i rebiuld the bike ill leave out the spacer to see what differnce it makes.thanks

[JDR215]

can these be purchased as an aftermarket item? and if so who makes them? if not i will whip one up myself, interested to see how well they work. how thick should i make it?

[ossagp1]

I am trying to remember who made them. ProCircuit I think did some. It would make sense. Check for pipe clearance. 1/4 of an inch seemed to be popular. They were only about 20 dollars, but we made a few out of some plastic that we used to make spacers for adding flywheel weights. Just see what your pipe will take clearance wise.

[JDR215]

yeh, i will have to measure it up, just so i know though, the bigger the spacer, the better the low end? or will it just be overkill? i am also thinking of trying out the exhaust pipe spacer, will these cancel each other out or will they work well together? does it sacrifice top end/

[ossagp1]

The bike we put the spacer on is my son's. He said it quits paying back before it hits the pipe on his 2000, which has a ProCircuit pipe on it(the procircuit has more clearance than the stocker). He said the stock pipe hit the spacer at about 3/16's of an inch. He put one that was made of 1/4" stock on with 3 gaskets and it cleared the PC pipe just fine. He spaced it further with more gaskets and said he couldnt tell a difference, but swears that he got more out of the 1/4" inch than the 3/16". I wasnt on the bike enough to tell very much. I don't think there is very much. I just credited the improvement to a 19 year old who was really optimistic about his modification. Besides, all the magazines said it worked!!

We never played with exhaust pipe spacers on this one. In the past I have cut pipes and stretched them both. Usually what I expect is small. I have never had a time where I got any extra gains after about 1/2". Just play until you like it or don't like it. Where as the length of the pipe on any expansion chamber is the most important SINGLE dimension, before long you run out of the amount of improvement that a pipe will make on your existing porting. Stretching the header usually does take some off the top. The spacer on the cover didnt seem to hurt topend from what we could tell. The Honda pipe is a really good one for the port design and timing. Makes improving it harder. In the past 20 years I have done more cutting and stretching on gokarts with no power valve than I have on motorcycles. We play with cylinder height at the same time on those. You can do some of that with your motorcycle too. That changes your port timing as you can figure.