Exhaust port: How much to raise it for iceracing?

100hp honda · Post by **100hp honda** » November 3rd, 2011, 8:48 pm

this was first day i put the engine back together just testing it. you can hear it dont like 5th gear very well in the sand. cpi with porting i did just dont do well at lower rpm. keep it spinning to the nuts and your good

. thats why i mentioned to you the tranny swap. dont have to deal with the gaps. i got a '91 5th to swap in. gonna swap in the '91 4th also. should work alot better

johnnytheswede · Post by **johnnytheswede** » November 4th, 2011, 4:51 am

Roostius_Maximus wrote:so your exhaust port timing is likely 184.4 to 185.1 depending on base gasket
stock cylinder is around 178

i'll check my book tonight and get back to you if i'm doing this wrong

Ok, great! Which gasket is thickest? I have an oem and an aftermarket but i haven,t measured them.

Johnny

johnnytheswede · Post by **johnnytheswede** » November 4th, 2011, 4:53 am

100hp honda wrote:this was first day i put the engine back together just testing it. you can hear it dont like 5th gear very well in the sand. cpi with porting i did just dont do well at lower rpm. keep it spinning to the nuts and your good . thats why i mentioned to you the tranny swap. dont have to deal with the gaps. i got a '91 5th to swap in. gonna swap in the '91 4th also. should work alot better

Nice movies! Yes, it is very noticable when the power comes in with the CPI pipe! probably too explosive power for me. I will look and measure the DEP pipe to see if that one is good. I,ve heard that meny like it with moderate porting.

Johnny

johnnytheswede · Post by **johnnytheswede** » November 4th, 2011, 5:23 am

Ok, i just measured my two different gaskets, and the factory gasket is 0,5mm thick. The other one is 0.45mm thick, so maybe i could run with two gaskets if i don,t want to port it more than i already have. I also have a 63cc dome for my Coolhead if i want to increase the comp. I guess a slightly lower comp will smooth out the powerband too. Kind to the bearings when iceracing on wot a lot too=).

Johnny

100hp honda · Post by **100hp honda** » November 4th, 2011, 8:58 am

did you use the epoxy in rear ports like eric said ?

johnnytheswede · Post by **johnnytheswede** » November 5th, 2011, 6:09 am

100hp honda wrote:did you use the epoxy in rear ports like eric said ?

No, i actually just about to finish the porting on the transfers, and as i,m no pro at this i do the regular port raise and try to get the angle slightly better for top end power=). I think that would be good enough for me.

Johnny

100hp honda · Post by **100hp honda** » November 5th, 2011, 12:05 pm

shit im no pro by any means either. if you have the right tools and some common sense you should be fine

johnnytheswede · Post by **johnnytheswede** » November 5th, 2011, 2:43 pm

yes, i use a 90 degree angle grinder and do the work with different stones, but it, a real PITA to get through everywhere, and to measure the roff angle in the transfers is no easy task, but i think it will be close to standard at least. It takes time, but who needs to hurry;=).

Johnny

100hp honda · Post by **100hp honda** » November 5th, 2011, 6:45 pm

get one of these at the hardware store and a box of paper clips. bend the paper clip to the angle you want. then you cut the roof using the paper clip against the cylinder wall to measure the angle. make sense ?

put a mark approx this far in and thats how far back to cut the angle then blend the rest of the roof to that. its your decision how far in to cut but theres no need to go very far

should look something like this once you start cutting

finished product

johnnytheswede · Post by **johnnytheswede** » November 6th, 2011, 12:46 am

Ok, great! That was good information as i thought i had to cut the angle deeper in to the port=)! I think i have done it quite well then, because i took quite a lot of material off in that area. At least i think it,,s close to standard which is ok with the tools i have;=)! What angle have you taken yours too? Does it make a noticable difference on top revs? I guess it,s hard to say when there is more work done at the same time?

Johnny

100hp honda · Post by **100hp honda** » November 6th, 2011, 7:53 am

10-15* will work fine but you can put it more or less angle. seems like the floor shoots in 20* or so upward and i flatened that alittle also. your decision how to go about it

johnnytheswede · Post by **johnnytheswede** » November 6th, 2011, 1:30 pm

Ok, thanks! I just finished the porting and i tried to flatten the floor a bit so i think it,s a little more flat than standard. I also decided to take another 0,5mm on the exhaust port. I think this will match better with the transfers which i raised 1,5mm. I have just put the engine together, but i forgot to order new reed gaskets so i have to wait for that before start up and running in the Wiseco. What main jet do you think could be good at sealevel and around 50 degrees F? I have a 182 in it now, but was thinking of a 188 to be safe and check later.

Johnny

100hp honda · Post by **100hp honda** » November 6th, 2011, 5:58 pm

188 should be good for a start. not sure how you change the main but if you have a 17mm wrench and 6mm 1/4 drive socket with small vice grip pliers you can change it easy and dont have to mess with loosening the carb or turning it sideways. cut a milk jug or pop bottle to put in there so the gas runs out the side and not all on the engine.

http://www.youtube.com/user/500bigbore · Post by **Roostius_Maximus** » November 6th, 2011, 6:52 pm

100hp honda wrote:... not sure how you change the main ....

are you friggin serious?

100hp honda · Post by **100hp honda** » November 6th, 2011, 7:09 pm

im not sure how HE does it. was trying to help him how I do it so he dont have to loosen carb or tilt it or whatever. heard of guys loosen the clamps and turn it sideways. much easier ways that dont require all the extra work

johnnytheswede · Post by **johnnytheswede** » November 6th, 2011, 11:21 pm

I have messed a lot with the carb and jetting so that,s no problem=). Thanks anyway! I just wondered how much you think the porting will affect the jetting. I have put in the Power reeds too, so i guess i have to start quite fat with the new portjob and piston and run it in, and then i do the regular plug check. I also have the JD needles to use.

I really enjoy being on this forum and i,m very glad for all the help and opinions that all of you give me=)! I learn new stuff almost everyday. It,s not that i don,t have experience before, but all the in depth technical stuff about the 500,s that are special for them is of course new for me. I,ve been working a lot with cars before, turbocharged Ford Cosworth. We have a forum here in Sweden too, but not just for 500,s, but we are a small group of guys with 500,s who mostly use our bikes for iceracing=). We don,t have sanddunes like you!

Johnny

LOVEMYCR500 · Post by **LOVEMYCR500** » November 8th, 2011, 11:09 am

roost, if FMF won't reissue the fatty verison of the CR 500 pipe and it appears to be a good pipe, you ever consider measuring it then having copies made?

I would assume people would buy it. I'm looking for all around power pipes that perform better than the PC and current FMF gnarly pipe.

johnnytheswede · Post by **johnnytheswede** » November 8th, 2011, 11:35 am

Ok, i just put my engine together after the portjob and rebore and made the first run-in yesterday, and today i finished it. The bike feels really good, and can,t say i notice any worse bottom end power than before the portjob! It feels very "light" and revs clean and easy when i twist the throttle now. I did some wot runs and it,s very strong in mid revs and i feel that it wants to rev more, but i think the PC system is the plug. So what you are saying is that the fatty pipe is no longer available?. What is there to have instead of that one for more top end power?

Johnny

http://www.youtube.com/user/500bigbore · November 8th, 2011, 12:59 pm

here's something i've found, start with a main jet the same as the exhaust duration

johnnytheswede · Post by **johnnytheswede** » November 8th, 2011, 2:26 pm

Ok, so i should start with à 188 as a guideline then. Maybe it, à but lean on top with à 182 then at 45f. I try that and get back! Thanks!

BannedCR500Riders.com

Exhaust port: How much to raise it for iceracing?