Winter Madness Begins!
#13
11-09-2007 | 11:51 PM
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RE: Winter Madness Begins!
ORIGINAL: kgwld1
I also have the Weisco piston and my tolerance was spot on and no the don't expand as much as a cast piston.
I also have the Weisco piston and my tolerance was spot on and no the don't expand as much as a cast piston.
So keep this in mind. The 300 cylinder is bored and coated to accept a cast piston. You can't take any additional metal off without having to recoat it. So unless the Weisco piston is forged with this consideration, I would be cautious about running it with the same tolerances as the cast.
Good luck!
#15
11-10-2007 | 02:06 AM
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From: Misawa Japan
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RE: Winter Madness Begins!
ORIGINAL: vfrpilot
I'm not wanting to start anything here but forged pistons do expand more than cast. I don't know if this is an issue with 4 strokes but I would think that the same principles apply. On a 2 stroke with a forged piston you have to increase the tolerance by at least .002. If you don't you will always sieze a piston. That is why I can tell a rebuilt engine with a Weisco piston in it simply by listening to it run. There is a piston "rattle" at idle. If that "rattle" doesn't exsist then it won't be running for very long. I'm sure that someone will site the exception to the rule, but I have yet to not hear it. Whenever I have rebuilt an engine whether it was 2 or 4 stroke I have always went for the cast piston. This is only because of experiences that I have had with the forged pistons. The amout of extra tolerance needed is always a guess.
So keep this in mind. The 300 cylinder is bored and coated to accept a cast piston. You can't take any additional metal off without having to recoat it. So unless the Weisco piston is forged with this consideration, I would be cautious about running it with the same tolerances as the cast.
Good luck!
ORIGINAL: kgwld1
I also have the Weisco piston and my tolerance was spot on and no the don't expand as much as a cast piston.
I also have the Weisco piston and my tolerance was spot on and no the don't expand as much as a cast piston.
So keep this in mind. The 300 cylinder is bored and coated to accept a cast piston. You can't take any additional metal off without having to recoat it. So unless the Weisco piston is forged with this consideration, I would be cautious about running it with the same tolerances as the cast.
Good luck!
All I know is that, to date, I haven't heard of any issues with forged pistons on the KLX. That would include people I ride with thatrun a 315cc high compression kit sold here in Japan. The 331cc kit from Kustom Kraft and the 340cc from T/Ruse J.E. and Wiseco forged pistons respectively.Ican think of at least five people with the331 and at leasttwo with theT/R kitwhohave reported no problems. So far, so good I guess.
How about a weigh-in from those who own the big bore kits. Any issueswith seizure?Have you noted a rattle atidle?
#16
11-10-2007 | 02:12 AM
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From: Misawa Japan
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RE: Winter Madness Begins!
OK, but I'm still waiting for a comment to that effect from at least seven people in this forum who are currently running with forged pistons. If there were a problem with it on this bike, I'm sure I would of heard about it by now.
To date, there have been "EXACTLY" zero issues
To VFR's credit, he used 2-cycle engines as an example. Piston seizure is a much more prevalent issue with 2-stroke engines...expecially the air cooled variety. However, I disagree that the coating on our cylinder was 'bored and coated to accept acast piston' that is simply a false statement. That type of coating has been around in all sorts of engines running both cast and forged pistons.
To date, there have been "EXACTLY" zero issues
To VFR's credit, he used 2-cycle engines as an example. Piston seizure is a much more prevalent issue with 2-stroke engines...expecially the air cooled variety. However, I disagree that the coating on our cylinder was 'bored and coated to accept acast piston' that is simply a false statement. That type of coating has been around in all sorts of engines running both cast and forged pistons.
ORIGINAL: Beardoge
vfrpilot is EXACTLY right on this one !
vfrpilot is EXACTLY right on this one !
#17
11-10-2007 | 02:24 AM
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From: Lincoln Park,MI
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RE: Winter Madness Begins!
My bad after I wrote it I was wrong the reverse holds true, I must of had a brain fart! Due to the way a forging is made is where lies the diff. The forging is a lot stronger in theory and in practice. Once again sorry!
#18
11-10-2007 | 03:56 AM
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RE: Winter Madness Begins!
Tremor it is not a problem--I have the Wiseco & dont worry about it. I just take it easier on a forged piston engine when its cold since it may have a little more clearance.
Basically the only thing I have seemed to notice is a forged piston bike can tend to smoke on startup IF theywere get abused when cold, even if it is a realitivly fresh rebuild. Again, I let my bike warm up properly & have noticed nothing different than stock (except more power)
My statement was primarily based on what I have read in moto-rags & articles & yes they are most centered around ring-dings like VFR indicated. I would assume Wiseco is familiar enough with their own pistons & know about the stock bore of a KLX 300 to make a piston such that the required tolerances are built into the piston. Now on a two stroke that you bore out again & again etc. you probably need to be more careful as who knows what every Joe boring out the cylinders is doing. I also know it is not as big a deal as it used to be as they are refining the alloy used in the pistons to limit this (adding sillica rings a bell). Just my two cents.
Basically the only thing I have seemed to notice is a forged piston bike can tend to smoke on startup IF theywere get abused when cold, even if it is a realitivly fresh rebuild. Again, I let my bike warm up properly & have noticed nothing different than stock (except more power)
My statement was primarily based on what I have read in moto-rags & articles & yes they are most centered around ring-dings like VFR indicated. I would assume Wiseco is familiar enough with their own pistons & know about the stock bore of a KLX 300 to make a piston such that the required tolerances are built into the piston. Now on a two stroke that you bore out again & again etc. you probably need to be more careful as who knows what every Joe boring out the cylinders is doing. I also know it is not as big a deal as it used to be as they are refining the alloy used in the pistons to limit this (adding sillica rings a bell). Just my two cents.
#19
11-10-2007 | 12:40 PM
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RE: Winter Madness Begins!
One other thing that popped into my mind about this. All the instances that I used for examples were steel sleeved cylinders. It is entirely possible that the rate of expansion on a aluminum / nickaseal coated cylinder is more compatable to the forged piston. The more that I thought about it the more that it makes some sense. This may be why there seems to be no problem with no increased cylinder clearance.
Any thoughts on this?
Any thoughts on this?
#20
11-10-2007 | 01:39 PM
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From: Misawa Japan
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RE: Winter Madness Begins!
That makesperfect sense.I never thought aboutit from that perspective.Good call.
ORIGINAL: vfrpilot
One other thing that popped into my mind about this. All the instances that I used for examples were steel sleeved cylinders. It is entirely possible that the rate of expansion on a aluminum / nickaseal coated cylinder is more compatable to the forged piston. The more that I thought about it the more that it makes some sense. This may be why there seems to be no problem with no increased cylinder clearance.
Any thoughts on this?
One other thing that popped into my mind about this. All the instances that I used for examples were steel sleeved cylinders. It is entirely possible that the rate of expansion on a aluminum / nickaseal coated cylinder is more compatable to the forged piston. The more that I thought about it the more that it makes some sense. This may be why there seems to be no problem with no increased cylinder clearance.
Any thoughts on this?