Filling in exhaust port

[Onski326]

Is it possible to add material to the exhaust port roof? It's currently at 40mm from roof to head. I want to get it to around 45.
And if so, what should I use to fill it? Obviously probably not JB Weld.

[Pumashine]

Epoxy has been used for years. You can get certain ones that work great with aluminum. Of coarse your prep work will decide how long it will stay in place.

[Onski326]

Any preference to which epoxy would hold up the longest?

[udontknowme]

im not sure i would put epoxy in the exh port  :glee:. unless you can find one that will withstand the heat but i never could.  years ago i put jb welb on the outside of a pipe to fill a small hole and it basically melted off in a short time

[Onski326]

I was worried about that too. I've got some JB on a small hole on my CT pipe and it's been holding up well but it's halfway down the fat part so it's not really that close to the cylinder either.

[udontknowme]

crankcase, transfers, intake. most epoxies work fine in these areas. exh port is another matter


if it doesnt have a iron sleeve you can easily weld the roof lower. with sleeve im not sure if theres a filler material that can be welded to aluminum and iron simultaniously. could pull the sleeve out, weld the roof then install new sleeve with lower roof.

why do you think the roof needs to be 5mm lower ? i prefer to work in rotation degrees but 5mm sounds like alot in a short stroke engine

[Onski326]

One of my cylinder sits at 47mm. This one I have now sits at 40mm. Just wanted to scavenge some cylinder compression and gain some bottom end grunt out of it. I thought 45 would be sufficient but it is a lot of material. The port job wasn't what I would have wanted but it's what I have to work with. It's really hogged out on the exhaust port on the top and flared out on the sides. I'll try and get some pics tomorrow. Still on the bike at the moment but I'll be pulling the head in the morning if all goes well.
I wish I had a degree wheel but I don't so I used the best thing I could find to measure the difference. It's a pretty radical port job. Not sure who did it as there are no marks on the cylinder anywhere.

[udontknowme]

local bike shop might have a wheel. usually only $15 for the motion pro ones. ebay sells them also. ive also made temporary ones on cardborad with a protractor thing. like i said, using measurements from the top deck is a foreign language to me. i always use degrees. im sure if you can get the degrees someone can probly give you advice. might be able to shave down the base and get everything alittle lower but 5mm is quit alot

[Onski326]

Yeah. I kinda figured it might be too much. I'm running an '86 piston in it right now so I'm having to use a spacer plate and at the moment, my squish band area is at .045 so I can't really get the deck down any further.

[derby]

Your best bet will be to get a different cylinder and start over.  I have found that trying to make something work usually will cost you more in the long run and you will end up buying a new cylinder anyway.  If the cylinder does not have a sleeve you can weld the roof of the exhaust port but you would be looking at re-nik and some machine work.  If you have a sleeve it will need to be resleeved.

[Onski326]

Yeah. I just got this one used. Had it bored and cleaned up. Bought a piston kit, top end gaskets, spacer plate and then I run into this. Just didn't want to throw all away. If I can't fix it up a bit, I guess I could just sell the whole lot and restart this project...again. lol

[udontknowme]

$100 and it appears original  http://www.ebay.com/itm/Honda-Cylinder-bored-at-66mm-TRX-250R-1986-/251446526681?pt=LH_DefaultDomain_210&hash=item3a8b6182d9&vxp=mtr

get some pics and timings from your other one. someone here might want it or list it on ebay

[rsss396]

this will help you calculate your port timing from measuring http://www.torqsoft.net/piston-position.html#measure