CR head gasket and pump gas??

[YFZRob]

Will a CR250 head gasket raise compression enough to require race fuel? I would like to be able to go back to pump gas now that I'm going back to the stock jug, and to cut down on expense (race gas around here has gone over $6 a gallon from $4.49!). Not sure what kind of bump the CR gasket gives over the stocker. I've got both gaskets here, just not sure which to use. Thanks!

[2StrokeFreak]

You can try the CR gasket and do a compression test to see if its over 175-180. If it is put the stock 3-layer gasket on it.

[YFZRob]

Yeah....just did that, and I'll need the 3 piece :(. 209 psi on a COLD engine with extra oil on the rings and cylinder walls (for initial start up). That's on a fully broken in 66.5mm piston. Even with real world amounts of oil build up on the rings, I don't think it'll fall to 180. It'll probably be 180 with the stock gasket! I tried to measure squish with solder, but it wouldn't even start to flatten a .050" thick section of solder, so the squish isn't too low. I dunno. I've already torqued this gasket and have left over race gas, so maybe I should just fire it up and see if it goes down after letting it run for a little bit.

[2StrokeFreak]

What do ya got to lose? See how it goes on the good stuff for a while. 6.00 a gallon, I'd be running pump gas.

I have a cool head w/21cc dome, 3-layer gasket and am still getting 180 psi. and it hasnt been ringed in at least 3 seasons.

I run Amsoil dominator at 50:1
4 gal. premium pump gas and 1 gal. 110 leaded fuel.
Really makes it crack.

[wilkin250r]

Something doesn't sound right.

You said you are going to a stock jug, I assume you're also using a stock head? So you should be looking at nearly a stock motor?

Stock compression is somewhere around 165, a CR gasket should bump that a little bit, but not over 180. And you're measuring 209?!?

Not only that, but you're squish is over .050? I would expect much smaller if you're measuring such high compression.

Something isn't right, here. Are you sure your compression tester is accurate?

Get larger solder and find out what your true squish is.

[2StrokeFreak]

Whats the deal with squish? Using solder like plasti-gague I assume. What does this tell you other than piston to head clearance?

165 psi. on a stock setup is on the low side.
Book calls for 175psi. +/- 15%

[wilkin250r]

It doesn't TELL you anything, like you said, other than piston to head clearance.

However, that clearance is a very critical issue in controlling detonation. To fully understand, you would need to know exactly what detonation IS, and the factors that influence it.

I could type it all out, but it would be very long and boring. Instead, I highly suggest you read the article The Art of Squishing Things Till they Give (Power). (http://www.motocarrera.com/texttch1.htm)

The article is written about RD350 streetbikes, but don't let that fool you, the theory applies to any 2-stroke. The RD350 was the early basis for the Banshee engine.

[YFZRob]

Well, my assumption of the oil used for assembly on the walls and rings was correct. Just heat cycled it up to 140 degrees. Did compression test right after shutting it down... 179 psi. Looks like the CR250 gasket will live on this motor for now :-). Time to go riding.

Last night I was up till 2 am researching jetting a piped, stock jug motor. I decided to try the 38 A/S, CR250 reed cage, and TRX-5 since they are just sitting here. I dropped the pilot to a 42 and the DGH needle to the 2nd clip. Main is a 170. I'll unload it from the trailer and take it for a spin later and try some chops. I'm guessing the 170 main is plenty, especially with the race fuel in it now. Not sure if the needle is too rich or not, but I read that some have had good, non-fouling success with a PWK 38 A/S with the DGH needle on a stock jug machine. We'll see. So far, it sounds much tamer over the 310 kit. It has super crisp throttle response in neutral...almost better than the 310 set up, and vibration is down. I'm pleased!!

[YFZRob]

Upon more tinkering, I found an issue that someone might be able to help with...

I still haven't gotten it out on a ride, and it seems to run great in neutral except for one instance.....

If you let it idle for a few seconds or more and whack the throttle, it's got an off idle bog. It bogs for about .5 second and wakes up. If you whack the throttle with it just above idle, like coming back down to idle, it's fine...no bog. What portion of the carb would be responsible for an off idle bog? I shouldn't be too worried about it until I take it for a ride, especially seeing how an FCR carbbed 4 stroke will stall if you whack the throttle like that from idle. May just be exepected with a big carb on a stock jug??

[2StrokeFreak]

That off idle bog is why I recommend the 36mm PWK.

38 - 39mm on stock bore non-ported might run well WFO but I cant see it being efficient bottom thru mid.

Not to mention better fuel eco. with the 36mm.

[wilkin250r]

You don't really have an "off idle". Your carburetor does not see what RPM your engine is running at. If you go from idle to WOT, your are at WOT, regardless of whether the engine is racing towards the rev limit, or stumbling at 1500rpm. Just because your engine is sitting at low revs does not mean your carb is working on the idle circuits.

As far as your carburetor is concerned, "idle" is zero throttle, usually running on the pilot jet. A stumble from no throttle to wide-open may possibly indicate that you're a little rich on the pilot, or it just may be an unfortunate consequence of a large carb on a stock bore.

[YFZRob]

Okay, that's what I figured. I'm going to find out later today probably if the 38's going to be sold or not. I would rather have the 36mm, but I figured I'd try what I have first. I'm glad I did some research last night on the carbs though. I found out the OD of the inlet and outlet of the PWK 36 is the same as the PWK 38, so my CR250 intake and ESR reducer ring that I would have sold with the 38, will be a very nice benefit with the 36.

[YFZRob]

As far as your carburetor is concerned, "idle" is zero throttle, usually running on the pilot jet. A stumble from no throttle to wide-open may possibly indicate that you're a little rich on the pilot, or it just may be an unfortunate consequence of a large carb on a stock bore.

Cool...thank you for the reply. Since it's really not too much of a bog, I'll blame it on the big carb. I have a 42 pilot in it, which shouldn't be too rich, but who knows. The 310 had zero bog with a 50 pilot. We'll see later today if I can get it out around the neighborhood. I do like the more mild manners with idle, pipe fitment, vibration, and overall noise compared to the 310 kit. Everything seems right with the stock jug. Feels and sounds much more like an every day 250cc MX bike.

[2StrokeFreak]

You could always get your stock jug ported to match your pipe and 38mm carb set up.

I've heard good things about the guy on E-Bay out of Lansing, MI.
Good prices too!

But then you'r getting farther away from your goal of building a sedate fun ride for the wife, and somthing you will enjoy riding as well. Keep reliability in mind.

[baseballplaya23]

alright what does the cr head gasket get you? like performance wise? also what year cr gasket do i need for my 86 with stock head and cylinder?

[YFZRob]

Freak,

yeah......as much as I'd like doing that, it's putting me back to square one with the 310 kit. With just under 180 psi, I can burn up this remaining race gas and go back to pump gas. If the hit is too hard with the 38 and the TRX5, I'll get a TRX6 with the 36mm PWK like you have. That is assuming I like the power gains of the pipe and carb over the way it was stock (if I can remember 6 months ago). We'll see.

playa23,

I'm not sure what year to be exact, but even better, here's the OE Honda part number.. 12254-KZ3-000

It's a single layer steel gasket vs. the 3 layer stocker, so it bumps compression. Check your compression now. If it's 180 or so, you will not want to go to one unless you don't mind buying race gas. The slight bump in compression w/ the CR head gasket is probably worth 1-2 HP and a stronger bottom end/smoother "hit". I hate a mushy bottom end, so I'm a fan of running as much compression as possible while still safe on pump gas.

[baseballplaya23]

ya i dont mind running race gas so its alright i think i might have to do it. it doesnt matter what year or anything for my 86?

[YFZRob]

Shouldn't matter, as far as head gaskets go, it should be the same for all years.

[baseballplaya23]

alright thanks

[wilkin250r]

Originally posted by YFZRob
If the hit is too hard with the 38 and the TRX5, I'll get a TRX6 with the 36mm PWK like you have. That is assuming I like the power gains of the pipe and carb over the way it was stock (if I can remember 6 months ago). We'll see.

Nobody here likes them, but I bet an FMF pipe would be perfect for your needs. Smooth powerband, broad range. It generally doesn't make as much peak HP as other brands, but rather spreads it out over a much broader range. A true "all around" pipe.

[YFZRob]

Yeah, that's what I was thinking....and freak likes his. Plus they are CHEAP! Like $180 right now from RMATV. It'll match my Powercore 2 silencer anyway. My guess is that I'll end up with a FMF Fatty pipe and 36mm PWK :rolleyes:

[2StrokeFreak]

Rob,
Are you running a Powercore 2 with your TRX7 pipe?

I diddnt know they would work togeather if so.

[beerock]

rob your problem is the DGH go buy a CEL

dont waste your money on pipes and smaller carbs. the CEL will give you back th3e low end pep.

[YFZRob]

yeah, I've got my TRX5 pipe (no TRX7 made) running through a TurbineCore 2 silencer. I wanted a little less noise than the non-USFS ESR silencer. Except for the ESR center mount pipe, I think ALL 250R pipes will work with any brand of silencer, including stock, just like motocross bikes....pretty cool.

Beerock,

I'll order one up and give it a shot.....a lot cheaper than buying a 36mm carb if it works. Thanks!

[beerock]

go to

http://www.sudco.com/

and call them up.... there fast cheap and dependable.

I know it will help, i had a fully ported stock jug 250r with a dgh and it always fouled plugs when i was at 1/4 to 1/2 throttle and it would start to bog after 3-4 hours riding, i would just change the plug and be peppy again. but once i changed to a CEL it was night and day difference and the gain i got on bottom to mid was awesome. this was with a 39mm carb too so youll see better gains with the 38pwk a/s

[YFZRob]

Seeing how the CEL needle is much leaner, what clip position would you suggest? And why the CEL? There's about 15 needles in between the CEL and the DGH.

[beerock]

Originally posted by YFZRob
Seeing how the CEL needle is much leaner, what clip position would you suggest? And why the CEL? There's about 15 needles in between the CEL and the DGH.

i just edited my post.. look up...

always start in the middle....

[YFZRob]

Hey guys....

Took it out for a ride.....WOW!! At first with DGH needle on 2nd clip (from top) and 42 pilot it had a bad bog. Cruising on the pilot (under 1/4 throttle), then rolling into it, resulted in a massive bog. It was only fine if I squeezed into very softly. Next I tried out the DGH on the 4th clip. Better, much better, but still boggish down low when laying into it. Then I tried going up to a 45 pilot....that just made it worse. This time, I went back to the 42 pilot but tried the stock PJ needle, which is equal to a DGM. BAM!!! Barely any softer on the bottom than the 310 kit with the 50 pilot and DDJ needle on 3rd clip, using the pump gas dome. So I after a LOT of part throttle riding, I pulled the plug....not so good. Coffee with lots of creme :eek2: SO, I think beerock pinned it on the head.....CEL needle will do the trick most likely. Looks like the diameter on the factory DGM is too large making it too lean, even though technically it's a richer taper and only slightly leaner diameter over the CEL.

Anyway, I think the hit is mild enough and bottom strong enough to keep the 38mm A/S and ESR TRX5 pipe. Just need to get the correct needle in it. I may throw a 50 pilot in the carb with the stock DGM needle and see if the lean issue is more at 1/4 throttle or closer to 3/4 throttle. That'll help me determine if the diameter of the needle is the issue.

[YFZRob]

New update....

Since I really think the stock DGM needle is working, I bumped the pilot to 50 and main to 175. Went out and did part throttle plug chops, then replaced the plug and did WOT plug chops. PERFECT! Looks like the slightly richer pilot helped at 1/8th-1/4 throttle where it seemed lean. The 175 I think is a tad rich, so I'll drop it to a 172 and enjoy!

I'm a fool for not just slapping a pipe and carb on this thing to begin with. I'd honestly say it's 85-90% the power of the 310 kit. I never leaned out the 310 kit to ideal jetting because I was so nervous of lean seizures, but still.... a perfectly jetted UN-ported stock jug is very impressive with just a pipe and carb. It has GREAT overrev too!! The 310 kit would feel like it was falling on its face earlier in the revs compared to the set up now. I'm IMPRESSED!

[brokeitin3]

hey rob thats the same set up im running, only i still got the 42 pilot and a cylinder spacer plate.

[2StrokeFreak]

Good to hear yoy have it worked out. Now you need to give it a full day of hell, see what the fuel consumption is like.

Un-ported jugs do respond well to pipe and intake upgrades. Night and day over stock pipe and carb. Thats why I havnt torn mine down for porting yet.

[YFZRob]

hey rob thats the same set up im running, only i still got the 42 pilot and a cylinder spacer plate.

That's good to hear! I ordered up 4 needles from Sudco yesterday. The guy I talked to said the CEL needle is very lean, but may work. It's leaner from 1/4-3/4 throttle than the stock DGM needle, but richer from 1/8th to 1/4. Anyway, I picked up a CEL and three others that are slightly richer than the stock DGM, but still retain the D taper, and still a lot leaner than the DGH. They were only $5.75 each! I also picked up a 48 pilot, so between the 5 different needles that should all be in the "right" area plus all pilot jets from 42-50 and mains from 165-190, I should have no problem dialing it in perfectly.


As for fuel consumption, even if it's only 10% better than the 310 set up, I'll be pleased! The 310 was amazingly not that bad. I went on 25 mile rides without burning more than 1.5-2 gallons. The longest single ride I have ever gone on was 38 miles, so even with the 310 kit, it'd just make it. I'm hoping to go riding this weekend, so I'll post back the results.

[wilkin250r]

Originally posted by YFZRob
As for fuel consumption, even if it's only 10% better than the 310 set up, I'll be pleased! The 310 was amazingly not that bad. I went on 25 mile rides without burning more than 1.5-2 gallons. The longest single ride I have ever gone on was 38 miles, so even with the 310 kit, it'd just make it. I'm hoping to go riding this weekend, so I'll post back the results.

That's terrible!!! For crying out loud, man, you own a 250R, open her up! Let her run free!

I don't think I could even make it 25 miles with my riding style. I'm on the gas WAY too much. My rear wheels might spin 25 miles, but actual distance traveled is only 10. :devil:

[250r4life]

That does sound like an awfully long way. I do most of my long rides in the dunes, and i know that dunes will require more gas, especially since ive got it floored the whole time and am in a wheelie anytime i wont have to be turning... there is no way i can go anywhere near 25 miles... i carry around a gallon jug in my 6 pack rack...

[YFZRob]

Hey, it's a MINT 88R....not something I want to abuse the hell out of, also it screwed me with two lean seizures (well ESR did by suggesting 93 octane was enough on the TRX7 ported, pump gas domed, 310 kit). If you dropped over $300 on top ends in less than 5 hours of riding, I think you may not punish your 250R. The problem was listening to ESR over the phone instead of trusting the "98 octane pump gas" listed on the install sheet w/ the top end.....but where the hell do you find 98 octane PUMP GAS!! I figured it was a misprint since more than one person said 93 octane was fine......especially when my cranking compression during break in was only 170........it all has to do with PORT TIMING.....something that took me $300 of screw ups to learn.

Now that I'm back on the stock jug, I will beat the crap out of it. Plus the fact that I ride with 4-5 other guys/gals who are on 4 strokes, I need to preserve my fuel as much as possible. We'll see when I get a little more aggressive with my rides now.

[FoxRacing81]

My old R had the CR250 headgasket and I ran nothing but Sunoco 94 pump gas with no problems at all. I ran Pro-X .40 over and the CR250 gasket.

[YFZRob]

Justin,

Do you remember what your cranking compression was?? Thanks!

[FoxRacing81]

Originally posted by YFZRob
Justin,

Do you remember what your cranking compression was?? Thanks!

Ah!! For the life of me, I cannot remember!!!:( Sorry man...

[beerock]

rob, for every day riding you will consume more gas then a 310 and 330 believe it or not. its because they dont have to be on the gas as hard as you.


sounds great getting those needles. honestly you have to do 1/2 throttle chops to really jet it perfect.

with a 38 a/s you should have around a 48 in the carb. I run a 52 and never have any problems.


didnt i say the power would be a huge diefference???? :D

[300exQuadracer]

i just put together a la sleeve 295cc big bore and you mill the head to 26cc i have a fmf gold series fatty and a 38mm carb they say to run a 175-172 main 65 pilot and a DGJ needle and by the way you guys are talking i dont have the money to lean seize this motor this late in the season, any suggestions on fuel and jetting??

[300exQuadracer]

Originally posted by 2StrokeFreak
I've heard good things about the guy on E-Bay out of Lansing, MI.Good prices too!



are you talking about R B Racing

http://groups.msn.com/rbracingtwostrokeporting

[YFZRob]

175-172 main 65 pilot and a DGJ needle

Dear god!! A 65 pilot??!??!?

On the 295 "aka 310" start off with at least a 185 main, 50 pilot, and the 5th clip on that DGJ needle. That's assuming your at sea level, or close to it. You might be able to go down a little on the main jet, especially if you run race gas, but 185 should be the minimum starting point to be safe. Also, you will have to check your compression and squish area. If your squish is too low (under .040"), you probably will want to run race fuel, and if your compression is over 180, you probably want to run race fuel. Just listen closely for detonation. If you hear a rattle in the engine while in the powerband, get out of it.....you'll need more octane or more fuel.

[300exQuadracer]

the compression after break in is supposed to be 165
also 5th clip position is the bottom position right

[YFZRob]

165 shouldn't require race gas, but that still depends on port timing. Since you bought it from LA Sleeve, it's not ported right? Should be fine on 93 pump gas.

Yes, 5th is the bottom position.

[300exQuadracer]

i put the kit together i bought the sleeve and piston, and had a machine shop put in the sleeve,

thanx for all the info