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Gearheaderiko
| | Posted on Friday, January 14, 2011 - 08:33 pm: | 
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Your assumption would be correct and the conclusion I would've come too if I hadnt spent the time on the dyno and the track and have used other non-515 CP pistons with great success.
At least one other person that had the failure did cc the heads, "clayed" the head and given his racing experience my guess he didnt leave out any of the steps to insure the success of the "kit".
The valve pocket seems way over cut. I think they try to accomplish too much with the 515 piston, whereas the other non-515 pistons are just overbore pistons.
I'd never spend the money on a CP 515 piston unless they told me they modified the piston to eliminate the problem. I'd use their other pistons readily. But if someone whats to take a chance with their money and buy a 515 from them thats their choice. Hardly seems worth the cost or risk for such a minimal gain in displacement.
(Message edited by gearheaderiko on January 14, 2011) |
Ezblast
| | Posted on Friday, January 14, 2011 - 10:48 pm: |
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Right and to get XB sized valves in a Blast you would have to similarly reshape the combustion chamber to make them fit, which is even more work. Always bow to the less work, which would be the XB for larger valves, there was one change up on the Blast head though, or we would be using tuber pistons, never could get that hinted information - hostile source - lol - do you know?
EZ |
Jsracer
| | Posted on Friday, January 14, 2011 - 10:52 pm: |
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Gearheaderiko, I've seen pistons of every brand fail right there. It's certainly not unique to CP. It's the most common point of failure when you have detonation.
CP makes a LOT of 3-9/16 bore pistons and if there was an inherent problem in them it would be well known. Have you confirmed that the 3-9/16 bore (515) Blast piston is thinner between the upper ring groove and the valve pocket than their other 3-9/16 bore pistons like those used in 1250 kits?
To me, until you do that and you know for sure there's a difference in the design, it's all anecdotal. Personally, I'm skeptical, just because they would have no reason to make the Blast piston thinner there. It's just a different dome is all, otherwise it's all the same as a 1250 kit piston. But having not made the measurement myself I'll leave the possibility open. I just know from experience that pistons very commonly break there due to bad tuning and blaming the piston is usually wrong. |
Jsracer
| | Posted on Friday, January 14, 2011 - 10:55 pm: |
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Ezblast you lost me. A Blast does use a tuber piston. It's a stock Thunderstorm piston. CR is only 9.2:1 because of the short stroke. |
Ezblast
| | Posted on Friday, January 14, 2011 - 11:18 pm: |
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Thank you - that is what I was referring to.
EZ |
Gearheaderiko
| | Posted on Saturday, January 15, 2011 - 12:07 am: |
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Personally, I'm skeptical, enough not to waste or tell anyone else to waste money on a piston that seems prone to failure, especially when the gains are minimal.
The 515 I used was an XB piston, not a Blast piston and the only reason I bought it was because I had a race in 4 days and the 515 was the fastest way to get all the parts together and ready.
I've been beating on a CP .015 over Blast and XB piston for quite some time now and they show minimal wear.
I havent heard of any of the 3 13/16" 600 or 1200 big bore kits having excessive failures.
I dont think comparing the XB9/P3 pistons to the XB12 piston really proves any point. Maybe they just did a better job on the 1200 "big bore" pistons.
You say tuning error, I say they over cut the valve pockets. I'll pass on my experience, you pass on yours. |
Ezblast
| | Posted on Saturday, January 15, 2011 - 12:27 am: |
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JSR - unless you have a shop where you specialize in Buells, you just oopsed - lol - the real point is those 515 cp pistons have had consistent problems/failures, and that has tracked across all the Blast boards. The major reason Revolution offered another brand piston - with their kit version, a very hi quality kit at that.
EZ |
Jsracer
| | Posted on Saturday, January 15, 2011 - 10:35 am: |
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So neither one of you has ever actually made the measurement and shown that the CP Blast piston is thinner in that area than their other 3-9/16 bore pistons?
That makes your assertion purely anecdotal.
Every racer knows that pistons break there when the tune is wrong. Before you go blaming the piston you ought to at least back it up with some facts. |
Ezblast
| | Posted on Saturday, January 15, 2011 - 02:48 pm: |
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Ahh - so if your not a racer, you can't install and check a piston, or tune it on a bike? Your assertion sir - is ridiculous. This is more than just a few piston failures, it is a majority installed, making for a lucky minority - so far.
EZ |
Jsracer
| | Posted on Saturday, January 15, 2011 - 05:03 pm: |
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Ezblast, have you made the measurement or not? Is the CP Blast piston thinner right there or isn't it? Or are you just guessing?
The piston is the part that breaks when the tune is wrong. Any motor guy knows that. Only an amateur will see a piston break and jump to the conclusion that the piston was faulty. You won't see any motor builder who knows anything do that. Maybe it is and maybe it isn't, but you sure can't tell just because it broke.
I'm curious what the measurement is. Aren't you? |
Gearheaderiko
| | Posted on Saturday, January 15, 2011 - 07:41 pm: |
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Where's your dog in this fight?
You either work for CP or somebody who sells a CP piston 515 kit, or you're just trolling.
From your profile you dont own a Blast or an XB and you arent showing any credentials to back up your claims.
Right now its just a "is so", "is not" argument.
Blast and XB riders have money to lose on this one, you have nothing to lose (except if you do work or sell CP).
Its a fool that thinks, "well many of these break, but I know what I'm doing, so mine wont".
Its a gamble and I'm not going to spend time or money just to prove you right or wrong. You get the pistons and you do the measurements if you're so "curious". |
Jsracer
| | Posted on Saturday, January 15, 2011 - 10:22 pm: |
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So in other words you're not really interested in getting to the root cause of the failure. Fine with me.
To me, you've got two pieces of evidence:
1) you know of more than one piston breaking
2) the same company ships thousands of pistons in that size but with just a different dome and they don't have problems.
So you've got one thing that says maybe it's the piston and one that says maybe it's not. Yet you've made up you mind.
A good engine guy always looks for the root cause of the problem.
You must work for Wiseco 
One other piece of information for you. CP does not make a "Blast" piston. CP is a custom piston manufacturer. In other words they make pistons to their customers specs and the customer sells them under his own brand name.
If a company selling these pistons believes there's a problem, he doesn't have to switch brands. All he has to do is make one call to CP and ask them to make the pocket smaller or move the ring pack down. |
Ezblast
| | Posted on Saturday, January 15, 2011 - 11:45 pm: |
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JSR - we where just talking about this over BBQ - Terry P., Firemanjim, etc. - they are a custom piston mfgr, they will have a high, medium and low tolerance spec and they figure that the spec that either has the least or most material to the ring size is the surviving group, and the spec. for median and other edge tolerance is the failure group that it could well be a mfgr. spec. type error, however, the first thing out of Terry's mouth was that the tune would play into that failure rate as well, but even his experience with all the reports of Blast failure at the pistons with the kits tells him something else is involved, especially with so many experienced and/or dealership mechanics installing the kits. Jim mentioned that all the kit makers are going to flat-tops - nhrs, revolution, etc. - for ease of replacement parts? I was trying to follow their conversation, and find out more plans on Terry's bike - he has a pork-chop crank - balancing stuff, for more revs for a small stroke, rr largest bore piston/cyl combo - still keeping it to 650cc/8200rpm capability - animal stuff - he wants the 150 club for the Blast, then he will rebuild and see what he can do in the alterfuel/nitrious class - if it don't blow up it should be fun!
EZ |
Gearheaderiko
| | Posted on Sunday, January 16, 2011 - 02:08 am: |
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"A good engine guy" Thats how many times you try to insult and you're not trolling? Your very brief profile says you're hiding something.
When you have over 6000 miles of something working without fail through every kind of timing and carb problem and finally loses compression to ring wear. Then you have something else that doesnt last 500 miles through very close watch and you wonder. And through your research (not to mention taking the piston down to CP) of possible causes you find a whole bunch of other people with the same failure, you stop looking and go back to what works extremely well, rather than focus on something prone to failure.
Many of these failures are on very mild engine tune. The Blast is extremely forgiving to poor tuning and bumping up the compression to 10.5:1 is hardly close to extreme.
Happy now? Should we title this thread in your name? |
Ezblast
| | Posted on Sunday, January 16, 2011 - 02:58 am: |
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Or like most business groups, you sell your old stock, and then go to flat tops - for ease of stocking? - Thats what I heard - all the kit companies are doing it, revolution, nhrs, etc. - go figure - and Eric is right - usual hot cam - lol - was the B-50! a few the B-70/SE series, and the rest burned the candle at both ends with the higher cams - the 580 being the hard border if you wanted any engine longevity - as Terry told me.
EZ |
Crackhead
| | Posted on Sunday, January 16, 2011 - 10:56 am: |
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The problem I see with the cp kit that I saw, was the lack of recomendation on jet sizes to even make it through the heat cycles. The parts bike I melted the piston with oem jets in place. A 175 or 180 jet should be part of the kit.
The parts bike had a melted piston. Chunks are part of the head and cylinder walls.
The 515 kits are marketed as drop in replacements. And since the POS HD paper gaskets go bad, the 515 kit is purchased for a while I have it appart upgrade. Since the Blast demographics are mainly young and are used to EFI, they assume the carb can adjust for the slight change. |
Jsracer
| | Posted on Sunday, January 16, 2011 - 05:19 pm: |
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Gearheaderiko: If you don't think a good engine guy always tries to figure out the root cause of a problem, fine, no skin off my nose. It tells me everything I need to know about you.
Ezblast: As with your misunderstanding about stock XB and Blast heads being fitted with the same size valves, again I'm sure you heard wrong.
There are many different chambers in the world of Harleys and Buells and many different engine sizes. A flat top would result in very low compression in some applications (for example a Blast or XB9) and very high compression in others (for example an 883/1200 conversion using the stock 883 heads). What's more, under some chambers you'd lose the factory squish band, for example Thunderstorms. No shop is going to try to sell a flat top into all applications, not if they want to stay in business anyway.
Crackhead those are very good and insightful comments. |
Ezblast
| | Posted on Sunday, January 16, 2011 - 10:56 pm: |
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I'll ask again about the kits, Terry will know as well - we have some horse trading to do, but the 515 cp kit piston has had way more than its fair share of failures, forcing companies to add alternate pistons to the Blast kits -
EZ |
Ezblast
| | Posted on Sunday, January 16, 2011 - 11:09 pm: |
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Oh - and on the valve size thing - I was right! - lol -
EZ |
Gearheaderiko
| | Posted on Monday, January 17, 2011 - 02:32 am: |
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A "good engine guy" with way too much time on his hands and no common sense.
2 pistons both producing almost identical power.
1 has a reported high failure rate at low mileage, the other ran for thousands of very hard miles without failure.
Both are CP pistons.
hhmmm....I think I'll spend a bunch of time and money trying to make the high failure rate piston work.
Makes perfect sense. 
I've actually done the research (until it became pointless) and have the piston. You are good at paraphrasing NRHS literature. |
Jsracer
| | Posted on Monday, January 17, 2011 - 10:32 am: |
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>> Oh - and on the valve size thing - I was right!
Well, maybe I misunderstood, I do have a hard time understanding your posts. But I thought you said that a stock XB and a stock Blast head could be fitted with the same size valves. If you said that, you're mistaken.
It's major work to take a Blast head up in valve sizes and it's even more major work to take an XB head down in valve sizes. So if you fit common valve sizes to the two heads, at least one of the two heads isn't going to be "stock" anymore. |
Jsracer
| | Posted on Monday, January 17, 2011 - 10:35 am: |
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Gearhead: I get it, you're sure you know the answer and you don't want to take the time to make the measurement to verify. Understood.
Personally I don't think a good motor guy operates that way, but do whatever you want, it doesn't matter to me. |
Jsracer
| | Posted on Monday, January 17, 2011 - 10:45 am: |
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>> but the 515 cp kit piston has had way more than its fair share of failures
Well, again, there's no such thing as a 515 kit CP piston. CP custom makes pistons to their customers specs. A CP piston you buy from company A is not the same as a CP piston you buy from company B, even if they're for the exact same application.
But that aside, what's the sample size? How many kits have been sold, and how many have failed? Unless it's a meaningful sample size it's just anecdotal.
>> forcing companies to add alternate pistons to the Blast kits -
Again, if a company thought they had a problem with their piston as CP was making it for them, they could fix it with one phone call, they certainly wouldn't be forced to change vendors.
There are a bunch of reasons for changing vendors ... price, service, quality, other business relationships, etc ... but a piston design that has valve pockets too big is not one of them. That's not the piston vendor's responsibility, that's the responsibility of the company that specs out the piston. |
Ezblast
| | Posted on Monday, January 17, 2011 - 06:57 pm: |
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Well I only know personally of a couple hundred kits, most where professionally installed, and of the installed at home group, most of the ones I knew of where real wrenches, or of a family of such. As for the spec.s, if it is used as a generic, and never, reviewed, it still falls into design error, not installer error.
EZ |
Dirtfarmer
| | Posted on Tuesday, February 08, 2011 - 09:43 pm: |
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Hey all. Thanks for the great info over the past year I've had my Blast. I'm ready to give in to the Dark Side and have a couple of questions. Will the XB12 cyl, piston, head, cam combo work? From what Erik has posted I'm thinking only the XB9 piston and cams will work, but I'm not sure. Ideas? Thanks in advance! |
Dirtfarmer
| | Posted on Tuesday, February 08, 2011 - 09:48 pm: |
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Not knowing XB's, will an oil cooler from a twin fit on the Blast? Thx again |
Gearheaderiko
| | Posted on Tuesday, February 08, 2011 - 10:12 pm: |
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Use the XB9 piston. The rest of the parts are the same whether its XB9 or 12. I think post 2007 cams are a slightly different fit, but I dont remember. (I think it starts in 2008 when they use a different cam cover with a different oil pump).
A twin cooler will work though some of the hose fittings and lines are different as well as mounting. However, just about any twin oil cooler or generic multi fit 2 hose oil cooler will work as long as you can find a place to mount it. Its nothing special. It just needs to be able to stand up to the vibrations (which generally stuff made for Harleys will). |
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