gregrob

Awesome Kev. Thanks a lot

Good to know, Thanks Other than new domes and O-rings, is there anything else I should double check before putting it back together, that may have caused/cause a water leak?

No I haven't, I have however ridden a bike with one long enough to know I didn't want to own one, ever, for my purposes. I'm not professing to be an expert on them, other than knowing they kill the ability I have right now to let the clutch out on either of my 4mils with almost no throttle and just take off. It's an expensive thing to "try" unless you're building a max effort drag bike. There was a guy on planet sand trying to trade one straight across for a stock ignition. It obviously didn't work too well for him either.

Water leak, hmmm... There was no sign of that on the dome and the O rings were in good shape, but it's possible. I wouldn't be surprised with the way the aluminum powder packed into the edges of the dome and sprayed on top of the rod. Almost like it has moisture to make it stick..

I had thought about it. I ran almost a gallon of premix through the cases and still getting metal shavings out... Would you clean the bearings out and run it or put new bearings in? Trying to get it going for this coming wknd. :-/

Here for pics http://cgi.ebay.com/ebaymotors/Yamaha-YFZ-...271410003r30393 It has a pickup coil type system that goes over the crank snout and has a sensor on the crank. From what I know. I dont know a ton about them, but I do know you will hate life tryin to ride it unless you want to redline it every time you take off.

Forget it unless it's an all out drag bike, and even then I wouldn't run it, but plenty of folks do. It's a complete aftermarket ignition system that essentially doesn't have a flywheel, so the torque loss is huge.

Well I promised I would post neat-o carnage pics when I tore it apart and here they are. My theory on what happened from looking at the piston is that the bowl sucked dry and started a lean condition, which caused the cylinder temps to sky rocket. The high cylinder temps started uncontrolled detonation, and that's what burned a hole through the piston. The reason I say that is because you can see two distinct and seperate areas of damage on the piston. The first being melting / deformation of the aluminum on the crown of the piston on the intake side. The other being the damage directly beneath the spark plug and the exhuast side of the piston. I believe the intake side damage was from being lean, and the other from detonation. Thoughts? The good part about it is that it burned a hole so quickly through the piston, and made such small particles that it didn't hurt, scratch, or gouge the cylinder wall at all! The cylinder looks great, and the dome even looks great except for a small amt of aluminum powder packed in a few places that could be easily removed. As I suspected before teardown I dont believe this was a jetting or timing issue, as the other piston looks BEAUTIFUL. It was a nice light caramel color all the way across the piston, indicating a nice even burn. There is ZERO pitting the piston top, crown, or the dome. Everythin on that side looks awesome. Piston-to-bore clearance checked in at .0045 so it's completely runnable. Just gonna get a new piston for the right side, base gasket, domes, and O-rings and put it back together. Next chore is getting all the metal out of the crank. Been filling the crankcase and washing out with 16:1 premix and the crank smoothed up a lot and got lots of metal out, but theres still shrapnel in there. Guess I'll try some cheap 2 stroke oil from walmart and see if it will help suspend the particles better than gas. Here's the pics: Plug Plug again Piston - Top View Piston - Intake Side Piston - Exhaust Side Piston - In Bore Other piston in bore Note: I carb cleanered the top off the piston and wiped off the nice carmel brown color it had going on

Uhhh why not just put a bigger motor in it? Bump for a nice bike tho, I think I see my old Marvin on there lol

Depends on if you buy them new or used. I would just run in frames but that's up to you. You can find them used anywhere from 325-450 but they dont seem to be on here all the time. Just have to keep your eye out. New they're 650-700 I believe. Another thing I thought about regarding your build is if you are buildin a drag bike, you should just get those domes from Kubitza and actually run methanol.... Here it's half the price of race gas so it equals out even though you use more, and the power is WELL worth it dude. I dont know if you've ever ran meth or not but it is the real deal. Not as difficult to setup and run as you might think either. I have a FAST drag ported motor and I have ran it both on methanol and race gas and it is WAAAYYY down on power when runnin race gas. It definitely does the porting no justice because when it was on meth it was one bad mofo for a 4mil. Just my thoughts , but when/if you do switch to meth you'll just wonder why you didn't do it from the beginning. I would NOT run meth on those T-5's though, they won't let it turn the rpms and give it the flow it wants on meth. I've tried that.

Depends on the percentage you mix it. I would give a rough rough guess of 2 main jet sizes for 10-15% mix Just a rough guess though

I think Shearers will run better on that porting and for what your doing. My in frame shearers ran a lot better than the oof cpi's .02

It seems to me it would be a hell of a lot easier to mix in some methanol if your sole intent is to boost octane cheaply. Old timers have been doing it for a long time. Just adjust your jetting for the percentage you plan to run. BTW methanol is 127 octane ;-)

Im not a builder or an expert so Im mot sure Im qualified to respond, but I can give you my opinion having been there and done that.. First I had a bone stock bike other than FMF fatties and a rejet. Then I had basically the same mods you do but w T-5's Next came the HJR dune ported 4mil, 34mm carbs, kept the T-5's and ran it on pump gas. That set up was nice, quick, amd torquey. Only problem I had was if beating on it in the hillclimbs/treeshoots it would overheat. Cooling system was in tact, I was just working it too hard in the boggy wet sand, low speed 1st gear pegged riding (no airflow), and steep steep ass hillclimbs Next step after that was where it is now, shearers and 35.5 mikunis running it on methanol. If I had it to do over I would skip straight to the last step obviously. I love it! You would like a ported 4mil on T-5's though, will get around the dunes really well and can fly if setup right. Just let your porter know what you're going to run and have him set it up w that in mind and it will do good. I wouldn't waste my money on pipes that were optimized for stock porting, since thats really where the power you're wanting comes from. I'd go for a 4mil if you can, if not get your stock cyls ported and a set of T-5s and a 28-32mm carb and set it up right and it'll run hard. .02

Dude, its this simple. Youre really overcomplicating, and others arent helping 1) GET A NEW SET OF DOMES FOR YOUR BUILD 2) IF JEFF IS OUT OF TOWN GET THE FROM BRANDON. HE KNOWS WHAT HE IS DOING AND CAN HELP YOU OUT WITH NO PROBLEMS. There is a lot that goes into domes amd if you were drag racing for money it might be worth it to have a CUSTOM set of domes cut. Most of the domes youre gonna end up with are gonna be cut by dave noss anyway. Some builders might spec custom domes for every build, b but I highly doubt it I know Kevin Herr doesnt, the ones in my duner are "off the shelf 4mil GAS domes" If you plan to run race gas, tell Brandon that and he will take care of you. BTW you're gonna hate that drag porting if this is a play bike. If you do NOTHING but drag race, then you'll love the cylinders .02

Comeon Mark, school us

Could be lots of things, what have already checked? I would make sure it's getting spark. Check carbs Check REEDS Compression check dead cylinder More than likely it's in the carb/reed area somewhere. When the bike fires on once cylinder stand up on the pegs and shake it back and forth from one side to the other. I find this sometimes brings the other cylinder to life. Could be a sticking float or something like that. Plug wet with gas? Spark plug gap correct? Pickup coil gap correct? (althought this would probably affect both cyls I would check it, and set it if you didn't) Just double check everything and you'll find it.

Maxima chain wax is the best I've personally used. Just put it on about 10mins before you're going to ride to give it time to setup and it will provide good lubrication without being sticky. I literally ride where the chain is dragging in the sand all the way up the hill and it will just clean off at the top. Not sticky at all. Good stuff in my book. Help the NON O-ring chain last for going on 2 years plus how ever old it was when I got it. Oil it before and after every ride and that chain held up better than most O ring chains I've had.

Who says / how do you know this?

I'd be interested to see some pics when you can post them again. Do the cascade stuffers act as a spacer? I think I'll need a spacer when I get my carbs back from Kim with the billet bowls on them.

Thanks, So a good option would be one with an internal crossover but without the fancy stuff in the intake tract. So just port that out smooth? and ideal would be internal crossover plus intake that matches your reeds?

I meant tie rod ends. They are ball joints but he needs to use them for ti rod ends lol. Hes the tie rod end punisher

Uhh, I've had them all and I would just setup a banshee for the way I wanted it. The yfz was fun but I was pushing it wide f'n open all the time, and it got boring.

35mm pistons? Really?

and we have the straight through design like this, with no fancy design in the middle... Which is better, and why?