10:1, 10.5:1, or 11:1 and FCR vs 450r carb

[WoodTRD]

I'm getting ready to do my winter rebuild and have a few decisions to make. I like the power of my ex right now with my stg1 hc, mild ported head, xr400 head gasket, ported stock header, pro circuit slip on, uni filter, +6 degree key, and no choke. It's pretty "snappy" is how I guess I could describe it best and has no problem keeping up with most 450's or pulling the front tires up a little in 5th with stock gearing. BUT it's recently started ticking/clattering like a sewing machine and isn't the valve adjustment, and it smokes just a hair and spits a tiny bit of oil out the exhaust so I've decided to rebuild it just to be on the safe side.

I'm going with new timing chain guides and crf450 timing chain (02-06 right?) to eliminate that as a possible source of the top end noise. The decision I'm facing is do I want to leave the key in and go with a 10:1 piston, leave it in and see how it runs with a 10.5:1, or take it out and go with 11:1. I'll be using a xr head gasket so the compression will be a little higher. I'll be adding a fan to the oil cooler and possibly some scoops if I run across some for a good deal, but I'm not sure they'll do anything. Will going to a 10:1 even really be noticeable? Just looking for some opinions from people who might have ran various setups. Of course something in the back of my mind is saying to go with 12:1 and hd studs too haha. I plan on getting a 450 or 250r within the next few years and keeping this one as a woods bike though so I don't want to have to baby it.

My other decision is FCR vs 04-05 450r carb. It seems FCR would be best for overall power but is it really worth it? I'm assuming they're more of a pain to set up/get to fit on a ex than the 450r carb...It seems like a lot more people have the 450r carb than a FCR, is it due mostly to price/ease? As in the 450r carb would be better bang for the buck and less of a headache?

[ish416]

Go 11:1 with no key. HD studs for peace of mind.

The air scoops do nothing. They are for looks. I had some and measured my temps, they were within 3 degrees with or without. The lower temp was actually without them.

Go with either a larger cooler, a fan or both for cooling.

As for the carb, I have ran both and I prefer the FCR. It's smoother and lighter on the thumb than the 04-05 carb and I think has better throttle response. Power wise, I think they are very close with the FCR pulling better on the topend, could just be jetting. The 04-05 was much easier to get dialed in I thought than the FCR. Price wise, the 04-05 is typically cheaper and doesn't require an adapter, unless you get a Sudco like mine.

[beastlywarrior]

what carb does the 04 05 450r use

[CJM]

Originally posted by beastlywarrior
what carb does the 04 05 450r use

keihin style think 42mm, FCR is usually 39 or 41mm Ive seen used before.

I would do an 11:1 and remove the key. In all honesty the key doesnt do a heck of alot, yea its slightly snappier but nothing to write home about.

The best build is as follows: 11:1 piston, cometic brand MLS multilayered steel gaskets (they are metal coated with a special rubber and hold up better than anything else), stage 2 hot cam (although stage 1s pretty good) and a carb. Also going to an outerwears or no lid helps greatly too.

Bore size is relative, will you gain a bit if you go from stock to 407 or 416, sure. But Id go with a 407 b/c if you need to bore again then you at least can bore it 2 more times till you have to do a 440. Compression is power, not bore size, bore size gains slightly, compression gains ALOT.

IMPORTANT: If your going to change the guides and chain, change the tensioner as well. Im amazed my original is still good, but you can never be to sure and its worth just replacing.

[ish416]

The 04-05 carb is a piston valve carb just like the stock EX carb. Only major difference is that it flows more.

42mm vs 35.5mm or 38mm depending on where you find the specs for the 400EX. It is I believe a 38mm.

The 06+ Honda 450R runs a 40mm FCR. The Yamaha YFZ ran a 39mm FCR.

[WoodTRD]

Sounds like removing the key and upping the compression more will be the way to go, now I'll have to see if I can find my stock key. Any idea if flipping the sparks key around would be ok to get back to stock timing? I don't see why it would be but I'm no expert.

I'm definitely adding a fan, it'll be nice if I can figure out a way to rig it up to a thermostat reading off the oil temp. Anybody know if there are still any bolt on larger cooler kits around? Don't think there are any local shops I could get more lines made at for a custom install.

If I install the HD studs I'll have a strong inclination to go ahead with a 12:1 piston, how does yours run ish with the 12.5:1 and xr cam? Any heat issues? What octane do you run? 93 is everywhere here and race gas is available but no e85 that I know of. My bike probably sees about 20% sand, 30% mx track, and 50% woods. I was planning on either a 406 or 416, the higher compression I go, the more ill lean towards 406. That'll be 86mm right?

CJM I've checked my tensioner to make sure it's good, it spins out like its supposed to and everything seems up to par with it. Might be worth it to go ahead and replace for peace of mind though. My chain actually doesn't seem loose that I can tell, if I let the tensioner all the way out and stick it where it goes there's still about 1/4-3/8" of "adjustment" left when the tensioner hits the guide if that makes any sense. So I'm not positive the chain is where the noise is coming from but don't want to take a chance on it slipping or breaking and BOOM goes the top end and head I spent too much time porting.

If the cometic gaskets are the way to go over oem xr I'll go that way, do you know if they make a MLS head gasket the same or less thickness than the xr one? I'm convinced getting the squish closer to what it's supposed to be with the xr gasket is another part of the reason my bike runs so good...nobody believes me when I tell them it's still on the stock piston.

I made my own outerwears lid, basically cut two big holes in my stock lid and glued/made brackets and bolted a sheet of outerwears over it so it's getting plenty of air. The woods here are entirely too muddy to run no lid, I was having to clean my filter after every single ride without one and just didn't feel safe enough...and I don't trust my foam uni in the sand without a lid.

[CJM]

Anything over 11:1 is pretty much race gas only. 11:1 and under can use 93 easy.

Your tensioner sounds good, Id leave it be then. Could be your valves need adjustment is where your noise is. Id replace the chain and guides tho just for piece of mind. FYI the one guide comes out easy, the other you need to remove down in the clutch side case.

HD studs are recommened, due to extreme heat b/c of air cooling the exhaust side head studs usually will pull out. 100 dollars of insurance (if you buy them and have GT Thunder do them) is worth it imho.

Not sure of the thickness of an XR gasket, but I know the cometic is about .025-.027. Its all I have ever run since I rebuilt mine and trust me its got power.

[ish416]

I would guess that the Cometic and XR gaskets are of similar thickness. When I built mine all of the engine builders where suggesting to run XR OEM gaskets. I actually talked to Mickey Dunlap of Four-stroke tech and that is what he recommended on all builds under 88mm (426cc) and 13:1.

All of the aftermarket piston manufacter's that I am aware of: Wiseco, JE, and Namura all base their compression ratios off of XR400 engines (gaskets). The EX gasket was thicker resulting in a .2 - .3 drop in compression. So your 11:1 Wiseco or JE piston would actually be 10.7 - 10.8:1 with the EX gasket and become a true 11:1 with the XR gaskets.

As for compression, I have ran the 12.5:1 for many years. First I started running it, I was running VP C14 or C16 when I was racing, then switched to 100LL AV fuel then to E85 and now I am thinking about going to a 426 11:1 so I can run pump again. I never had any issues with heat on the stock cooling system.

I had friends who ran 11:1 EX's of various bore sizes and mine was always the quickest. However, theirs seemed to have slightly more pull on the top end, mostly because of larger cams, (stage 1 or 2 Hotcams). What mine did have that theirs didn't was diesel like torque. Enough torque to pull the front tires up at 20 - 25MPH in 5th just leaning back and getting on the gas. No clutch, no yanking on the bars just pure torque. That was on stock gearing 15/38 with 20" tires. The only other quad I have ridden that can do anything close to that is a built Raptor 700.

Yes, a 406 = 86mm piston.

I honestly don't think there is any advantage of going past 11:1 on the EX, unless you throw in a really aggressive cam and head work. Even doing that, you would still get pulled on easily by modded 450s so there is no point.

11:1 Cometic gaskets that CJM recommended or XR OEM gaskets will get you the compression you need. You already have the Stage 1 Hotcam, so you are good there. You have basically everything else except the cam chain guides and CRF cam chain, new tensioner and the carb.

Either carb will add noticable power to your build. I think the carb is the next best add on after compression. Either will put down similar numbers so get whichever you want.

[d90rick]

Would u recommend putting in an 11-1 piston, stock bore, before putting in a cam? Already hv sparks pipe, airbox, timing key. Ready dunlaps article i kinda get that is what he would advise for a woods bike

[d90rick]

Would u recommend putting in an 11-1 piston, stock bore, before putting in a cam? Already hv sparks pipe, airbox, timing key. Ready dunlaps article i kinda get that is what he would advise for a woods bike

[ish416]

d90rick,
I would go with the 11:1 piston of whatever bore you decide to go with first before the cam. If you go stock bore, you should hone the cylinder.

Also, going 11:1 you will need to remove your timing key.

[WoodTRD]

I've settled on getting rid of the key and going with a wiseco 86mm 11:1 like everyone seems to recommend, having to have race gas on hand seems like too much trouble for not enough gain. If I can get the thinner Cometic head gasket in a kit I'll definitely go that way, if not I'll most likely run the xr gasket (pretty sure its .27 too). Either way I'll run without a base gasket too if I think I can get away with it.

I'll be adding a 4' SPAL puller to the oil cooler when one comes back up on eBay, I only see pushers on there right now and not sure if the blades are directional or if just swapping the wires would work ok to make it a puller.

Definitely changing the timing chain for a crf450 and guides too. Most likely getting HD studs too, a local machine shop should have no trouble putting them in while the cylinder is there to be bored right? I want this to be the last time I pull the top end apart for a long time.

I decided to go with a 05 450r carb, found one ready to swap in for about $75 cheaper and less headache than I could get a FCR for.

After this round of mods I plan on being done with the motor, seems like its about as far as I want to reliably take it, think I've pretty much covered all the bases. If I still need more it'll be time to start saving for a 250r/450...but I don't plan on ever selling my ex. Too good of an all around bike to let go, it can handle anything I throw at it.

[CJM]

Machine shop here had no issues doing mine and a friends studs. I originally had GT Thunder do the bore and studs for me for convenience.

[WoodTRD]

Ok cool, I doubt mine will have any issues with them and it'll save on shipping having it done locally. Now if Uncle Sam would just hurry up with my refund I could finish ordering parts and get this project going.

[PrideRider]

sounds like you got a good build and good opinions CJM helped me out with great advice..advising almost close to what you are doing...crf 450 timing chain is a good heavy duty chain i would go with... if you dont have get a CFM oil tank 100 bucks cant beat it. just my 2 cents you will love it!

[WoodTRD]

Yea hopefully it'll be fast and rock solid, most of my friends i ride with have swapped to either 450's or 700's by now. Hopefully this will put me even or out front of their stock or piped bikes. I've pretty much decided to go ahead and send my cylinder in to gt thunder and let them do the bore and head stud install so I know without a doubt it was done right.

I'll look into the cfm oil tank in the future, my funds are just about tapped out for now and I still have gaskets, crf timing chain, and guides to order, and a spal fan in mid march when they come back in stock. Hopefully this $600 or so will be worth it.

[JOHNDOE83]

The 05 450r carb Is the best for most power, you made a good choice;)