Do I need to run race fuel???

**WMX500_RACER** · 03-20-2005, 02:57 AM

Hi i have an 84 CR250 that i just got done building my motor in i did all the work myself and after boring it .120 over portting & polishing all intake ports and exhaust ports i also polished the dome on the head after all this i did a compression test on it today and it has 205 psi

and the head isn't milled. i am wondering if im going to have to run race fuel? any good info on what octane to run?

also i forgot to mention it has not been started yet and the rings haven't even seated yet. so it's gonna be over 205psi after that

thanxs anthony

**SoCalDesertRider** · 04-03-2005, 03:22 AM

Sounds like a real nice motor you built!

I don't know at what point you NEED to run race fuel, but I run 108-110 octane race gas, usually either VP or Sunoco, in both my bikes and they run better on the fuel than on pump gas. I took the head off the ATC and it was very clean inside too. My friend runs the fuel in all his bikes too and his are all stock new bikes (oldest is 2000). To me, it's worth it to run the fuel and synthetic oil in the bikes. The ATC has 5 or 6 seasons on the same top end and the cylinder is still in great shape

.

**WMX500_RACER** · 04-04-2005, 04:12 AM

yeah it sounds like a good idea since this post i found out what my compression ratio is 14:4.1 and i have to run anything above 104 but best results would be to run 112-114 octane. as of right now i have a friend in machineing school and i'm trying to get a long rod CNC'ed to build another engine for this bike with will stroke it up to a 295cc engine if you wanna see pics of my bike it's almost done and pics are posted under my 1984 CR250R

thanxs 4 your info

**SoCalDesertRider** · 04-04-2005, 06:12 PM

Are your pics in the Readers' Rigs section? If so, what page?

**WMX500_RACER** · 04-05-2005, 04:48 AM

no there here in bikersville look for post that says MY 84 CR250R

**SoCalDesertRider** · 04-06-2005, 10:35 PM

Hey I found them! The bike looks good so far. Have you got it together now? Oh, that chain looks too tight in the pic (?).

**WMX500_RACER** · 04-07-2005, 12:11 AM

no the chain is fine for some reason i guess they look tight like that if you look at the pics 250R nut put up in my post that chain looks the same i think it is that the bottom chain rides on the roller it takes up the slack. as for the putting it togeather that i did started first kick left it idel for a lil while then gave it a few shots of gas and antifrezze shot out the radiator the head gasket failed it is a copper head gasket and i think the problem was when i put it togeather i might have got oil or something on it a when i put gasket glue on it . it din't seal where i got oil on it and due to the very high compression it din't last well i just got done cleaning it up and was very careful not to touch the mating surfaces befor puting on the gasket glue so i'm letting it cure overnight 24Hrs and will try it again tomorrow. i hope this does not happen again other wise im gonna have to get another gasket made like the original if this needs to be done does anyone out there know a good Gasket sorce as for the time it ran it had a very Crisp crackel to it and the throttle response was right there so hopfuly tomorrow i can take it for a ride with no problems i'll let you know tomorrow the good or bad news

Anthony

**SoCalDesertRider** · 04-12-2005, 01:33 AM

Glad you got it together. Sorry to hear about the blown gasket.

As far as I know, RTV silicone gasket 'glue' doesn't need to be used on our head gaskets. Maybe the silicone was the problem? I'm sure the oil didn't help either...

I used a CR250 copper head gasket on my ATC250R and didn't use anything on it, just cleaned the cylinder and head surfaces real good and torqued it to spec in a criss-cross pattern in 3 steps and no problems

.

Hope it works out for you, I know it's a bummer to spend a bunch of money and time and not be able to ride the bike. I'm still dealing with an overheating problem on the CR500, after putting both new rads, water pump and side case....

.

**jay72chevy** · 04-12-2005, 10:53 PM

hey this is wmx500 under my buddys name as for the over heating problem does it happen right away does it piss out the rads? cause i had a problem like that once with my CR it was the head gasket it was letting compression from the cylinder into the water jackets but the good thing it wasen't letting the water in the cylinder so it might just be the head gasket.. as for mine i think i found the problem i will know tomorrow i put a stright edge on the cylinder and head and and it dips in the middle and on the original head gasket it had like a pinch ring in the middle i guess that made up for the little dip so what i did is i took a belt sander to the cylinder and head and milled them flat so when i tighten the head down it's all flush on both surfaces so there no open space in the middle of the cylinder so i will post the good or bad news tomorrow

anthony

**SoCalDesertRider** · 04-13-2005, 12:02 AM

Hey that's great you found the problem! I had to have the head milled flat on my ATC cause it was warped and leaking water past the head gasket too. Sounds like yours should be good to go now

.

On the 500, it warms up, then heats up, then starts puking it out the radiator cap overflow tube. I was planning to take the head off and see what the water ports looked like in the head and cylinder cause I suspect they may be clogged, since the rads were totally clogged up before I had them rebuilt. I will check the flatness of the head when I take it off and put on a new gasket if the ports look ok. If not, I guess I will be removing the whole cylinder and having the cyl and head tanked, (if that is what's done with aluminum). Hopefully I will find SOMETHING conclusive when I open it up. This overheating has been a real bummer

. Other than that, the bike runs great!

**WMX500_RACER** · 04-16-2005, 01:39 AM

well bad news once again but this time i got to take it up the road and back befor it blew so it must be getting flater i only got threw the first 3 gears SCARY FAST it was fish talein while in a wheelie in third gear so i guess i did everything right to build up the engine other then that i'm takin it to the machine shop to get the cylinder decked and the head milled so i get both surfaces perfectly flat and flush for the head gasket to make a good seal i'll keep ya posed on the results any luck on the 500?

**SoCalDesertRider** · 04-16-2005, 10:24 PM

I haven't pulled the head off the 500 yet. We spent today taking my friend's 250 apart so he can have his shock rebuilt and swapped rear sprockets between the 2 bikes so the 250 will have the bigger one and 500 the smaller one. Maybe tomorrow I'll tear into the 500 cylinder.

Your motor sounds like a real monster! Yeah if it was warped that bad, the belt sander probly didn't get it flat and even enough to make a good seal. I'm sure the machine shop will fix it right up for ya! Hope it goes well

.

**MTS** · 04-16-2005, 11:33 PM

with the copper gasket, when you install it put a thin film of copper coat anti-sieze or the nickel-coat anti-size on the gasket--- i hope when you refer to head gasket glue you mean the high-tack red spray on stuff you put on there,,,NEVER EVER EVER EVER!!! USE RTV/SILICONE ON A HEAD GASKET!

**WMX500_RACER** · 04-17-2005, 03:59 AM

my local bike shop said i should use THREE BOND stuff they said that what they use for all there head gaskets.

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Do I need to run race fuel???