deckheight

Yes, stock = flat. However, A lot of machined (milled) OEM heads are flat as well. Only sure way to calculate a CR is to get a dome volume by CCing it. Otherwise, like Spurdy said... Anybodies guess??? If you can, CC the head (better yet get a trapped volume) and provide an exh. port height. There are several people on here who can calculate a CR and CCR for you with that info.

Yup, inductive light, either plug wire. Bring the left cylinder to TDC and indicate the flywheel, install a pointer at zero and hook up a tachometer. OEM timing specs are 17*@1000rpm, 22*@3500 and 9*@10,000 if memory serves...

:cool: :cool: :cool: Spurdy da man!

Looks real good, little cleanup here and there, polish the exhaust and looking sweet! Good durations for an "all around power band" IMHO :cool: . Blow down timing should help compensate on the bottom hit from raising the exhaust. Sounds like your getting real good advise and how about that 90 deg. handpeice from C.C. :biggrin: Just curious though, how come you are opening the Bust before the main and 5th transfers? Not that it will matter much from a couple deg. in crank rotation, just don't normally see that. What are your plans for head dome volume and fuel? Good work...

Whats bad? Crank threads? Bolt threads? Both? Just take your time...

Assuming the cranks threads and nose taper are still somewhat decent... Use a new key, lap the wheel to the nose taper w/valve grinding compound to clean things up and torque it back on w/red loctite and an impact. And dont use some super wazzoo impact gun w/200psi or something...

Pretty accurate IMHO except for the gunking stuff up part. AV does leave lead ash deposits. IMP experience over the last 30 years or so using the stuff off and on... The deposits do not build up in a 2-stroke. Don't know about 4-strokes??? The FAA doesn't seem to have much of a sense of humor when air planes start falling out of the sky though. In fact, I am running AV again because of it's availability. Or should I say lack of availability of something else. I have had the top end opened up a couple time recently and noticed nothing unusual I would attribute to the fuel. At any rate I am happy with it... Again

In my world the definition of over-rev is any rpm beyond peak HP... The claim as I understood it is: Usable HP at 11,000 rpm on a 350 Banshee motor like it is no big deal or something. As well as an inference that by not doing so there is some type of defeciency in setup and/or tuning ability. I'll assume 350 parameters to mean: Any bore diameter short of re-sleeving an OEM cylinder and a 54mm stroke. Not requesting any black magic, super secret, medievel mechanic crap, just the basics for proofing the claim... Port durations, tuned exhaust, compression ratio or fuel octane requirement, etc. Not even asking for port time areas! Hell, leave the tuned exhaust part out until after the whatever. Short of that, three weeks is no problemo. I already know what it takes to make peak HP at 11,000 rpm with a 350 and it is a very big deal! Like I said...

You are correct in that the right tube on a Banshee generally runs a little hotter, thus it is more prone to deto. FWIW I believe, but cannot prove... The right side of the crank being the load side, the right combustion chamber tends to run hotter due to torsional twist of the crankshaft. Basically, the right side is running advanced ignition timing over the left from the twist. I think... Stagger your jetting and/or head dome volumes to compensate or just dont run that close to the edge with your CR to start with.

Not sure what happened w/the quote??? No smartass either, just calling BS! Snop, what I meant was your numbers are accurate IMO. I am waiting for the Koolguy details so I too can increase my usable HP in the upper rpm range with more over-rev :biggrin: I am assuming my combustion is screwed up since my current bike makes no where near 11,000 rpm in the real world and my HP an torque dop like a rock in over-rev not long after making max HP. Short of that, I would like whatever drugs Koolguy is using :happy:

What's the matter with you Snop? Don't you know nothing? :biggrin: :biggrin: quote name='Koolguyson' date='Mar 25 2009, 03:22 AM' post='975315'] I didn't say free rev. I said overrev. Overrev is an effect between combustion and pipe design. The more overrev a motor has the better it will perform as it increases the usable horsepower in the upper rpm range. Notice I said you can get a motor to overrev to 11k+. If you cant get a motor to make USABLE power up to, or 11+, then IMO you have a setup issue. Even my big twin makes power at 11k+. If you can't get a baby 350 to make 11k+...yikes. You can disagree all you want. I have plenty of dyno sheets that prove the theory. Now, if you are talking a single cylinder, like a 250r, then yes, 8500-9500 is all they are good for, but not a twin.

Say what? "I just explained how to check for an indication of problems for all the bearings on a crankshaft assembly, without splitting the cases... And you are kind enough to remind me that there are 4 main bearings... LOL! Might take a stab at reading it again... Bearing assemblies normally don't just all of a sudden fail, they typically do it gradually. That said, do you honestly think that even the smallest peices of hardened steel going through a combustion chamber will not leave a mark on aluminum? I have caught enough bearing problems (before actual failure) with the use of magnification to know that it is a valid procedure. In fact, it is the only way that I can detect failure early on and I have 20/20 vision up close. Magnification is also the only way that I can tell the difference between pitting and cratering. And no I do not personally use a 10X magnifying glass, I use something a little more "state of the art". However, being that most readers probably don't know what an otoscope is or have access to one... I suggested 10X glass. At any rate, you know what you can do with your OP junior:biggrin:

What he said... Line boaring/finish honing for main bearing is the main issue for mismatched case halfs.

Very well could be your problem??? Depends wether or not the petals are sealing under positive crankcase pressure. Warped petals, bent cages, etc. it happens sometimes... It is not uncommon for the petals to not sit perfectly tight against the cages when they are off the bike and being visually inspected either. With the air filters off and engine running... Do you have noticably more fuel "spitting" out the back of the right carb than the left carb? How do the left and right spark plugs compare? Is the right one noticably wetter before it fouls than the left? Your sure it is fuel fouling? The carbs are at least somewhat synced? Right plug still fouling when you swap the plug wires? Any reason to suspect a bad right crankcase seal?

LOL! :biggrin:

A bad bearing normally won't foul a plug unless a peice of something is stuck between the electrode and ground prong. At any rate, if you want to check the bearings... Take off the piston, inspect the little end bearing and wrist pin under good lighting with a 10X magnifying glass. Then visually inspect the big end rod bearing under magnification, then for vertical movement and side clearance. Also check the head and top of the piston under magnification, this will tell you if there is any "cratering" or "pitting" in the combustion chamber and general location. "Cratering" is from something going through the combustion chamber like tiny peices (sometimes not so tiny) or specks of bearing or bearing seperator that are actually pushing material out of the way. "Pitting" is where the material is just eaten away from detonation. If there is no visual indication of a problem or cratering it is almost certain the rod and main bearings are still good :biggrin:

I have not had any problems with .100"(or .120" either for that matter). But, the thinner the sleeve the more chance of something really bad happening :ermm: When you have hard detonation it is comparable to repeatedly smacking the top of the piston with a hammer. It shoves the piston around in the bore and sends sonic waves and vibrations through everything. Sooooo, when combustion chambers are detonating and pistons are grenading like yours in the pics, chances for bad things happening increase dramatically! Good luck

Start a new thread w/pics... Your minus .030" OEM head is the first red flag! Somebody here will figure it out, just need more info and pics if possible...

Listen to blowit.

ThreeBond 1211. Most bike shops carry it. Iif you can find 1211, Yamabond works just as good.

With pistons and cylinders installed. Mount a degree wheel on the crank nose, bring one piston to TDC with a dial indicator and index the degree wheel w/a pointer. Bring the other piston to TDC with the dial indicator, degree wheel should read 180 deg. at the pointer. Like has already been said... Classic detonation. Deto finally ate off the piston crown on the exhaust side, ring poked into the exhaust port and got chewed up. Increase your fuel octane or increase your trapped volume with larger domes. Your right cylinder is running hotter than the left (as usual on a Banshee). Left slug doesn't look too far behind the right on the deto meter either Stagger your main jets two numbers and/or stagger your trapped volume .3 to.5cc to compensate. Just from the pics and description... Probably needing 100 octane or so on the fuel??? Hard to tell for sure without an accurate CR.

I'm 100% sure also...

Yup, I have often wondered what a compression gauge reading made at a couple hundred rpm has to do with what is happening in a combustion chamber when an engine is actually running and making near max rpm... Nothing I suspect! On the other hand, I can understand why a lot of folks rely on them. Compression gauge numbers are easily obtained, the data is easy to understand and they do provide something of a reference point. Problem is, it is an inherently inaccurate reference point... Compression gauges do sell a lot of parts though... LOL! Not saying that corrected compression ratios are 100% accurate for 2-strokes either... Things like extremely efficient tuned exhausts thrown in the mix sometimes make it real interesting... But CCR's are what I use anyway :geek: Me thinks you probably won't hear from any of well known engine builders posting on this site defending their compression gauge tuning abilities either :ermm:

IMHO, I do not think cranking compression should play much of a role in 2-stroke engine tuning either. But a lot of 2-stroke people seem to think pretty highly of it for whatever reason. Measure your exhaust port height with a caliper from the cylinder deck to the top of the exhaust port and subtract the deckheight. In this case a Banshee with OEM cylinders and base gasket has a dechheight of .002". Then just figure your "corrected compression ratio" using this number. Exhaust and transfer port durations are referenced in degrees of crankshaft rotation very similar to a cam in 4-strokes. The geometric shape of the ports could be compared to a cams lift... kinda... Sort of... The reason for the corrected compression ratio on a 2-stroke "ported" cylinder as opposed to a full stroke or 4-stroke ratio should be pretty obvious.

You might ride one before you drop the coin... Power delivery on a Banshee is totally different than a 4-stroke and can be a "religous experience"... Kind of like the difference between racing motocross (yehaw!!!) and riding a Harley on the open road (yawn...). I would quit rather than ride a 4-stroke for most types of riding. But thats just me.