squish question

M

maxco

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I have a little mystery on my hands. First off this is a 2000 mountain max. I have purchased a peak performance head and am installing it now. So I unfortunately did not check what the squish was before I pulled the head off, but it was running with no problems. Here is part A. of the question. The previous owner has 5, yes 5 layers of gasket. I find this odd. does anyone know why you would put 5 layers. I seperated and counted them. Stock is 3 I have heard of removing the middle one for increased compression, but adding 2? I want to understand what was trying to be accomplished by adding 2 layers. Before you answer read on.... So I installed the head, according to instructions, with a brand new set of EOM gaskets whole (3 layers). I tighten them down. I check squish. I am not a mechanic, but read alot. I use the solder method as descibed. the outside cylinders are good .061 on each. The middle concerns me, I checked it at the wrist pin twice. .049. Now this is tight. The MM head is one piece. So I either jack up the whole thing. Or leave it. If I want to try and lift the whole head up one layer I could do that. The split apart gasket I have is saying it is .026 thick. So adding it would mean .075 in the center, but .087 on the outside cylinders. From what I understand .055 is where I want to be. I am thinking about taking the head off and installing 1 layer. Then re-install and check squish, but how bad is .049 on the center cyl? I want the increased performance, but I do not want a re-build on my hands. Help Please, and thanks for any response. :2strokes:
 
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If I am reading this right I would find out why you have a different reading
on the center cylinder before I would ever run it. I will tell you .055 squish
is about max for premium pump gas to be safe. I would not run that motor
like that. You have a lot of money in head gaskets in there. lol
 
Peak cylinder heads have removable individual head inserts. It sounds to me like the middle insert is tighter or less cc higher compression then the outside ones. The inserts usually have their size engraved on them...check that and I'll bet they are different. Get the number off the outer ones and contact Peak as You can get more inserts in various sizes directly from Peak at 1-907-240-4233...talk to Neil.

Hope this helps.

Bob
 
If side show bobs advise dont pan out I would lay a straight edge across them jugs. If some one had jug or jugs off they may have mixed and matched base gaskets. Center cylinder gasket could be thinner basically raising piston in jug @ TDC. They have have relized they screw up on base gaskets and tried making up for it with the extra head gaskets.
 
more information

I was out working on this while some of the advice has come in. Here is the latest. I checked the dome sizes all 20cc. So that is good, I also checked the depth of each one they are all the same. I put a straight edge across the top of the cylinder heads. Ding, Devil in a blue dress wins. The center jug is low. For now I added 1 single gasket (torn from a full,one thin). It evened them up. I have .65mm clutch side, .66mm middle, and .61mm exhaust side. I am not happy about the drop. The machine has run for 2 years with it this way. I do not like it, maybe I will pull the jugs off this summer and see if they put in different gaskets on the bottom, or if one jug is just short. I would think it would not run at optimum if the center jug were lower, but maybe it is such a small amount it obviously didn't seem to effect it.THOUGHTS? :2strokes:
 
one more clarification

I look back at my numbers and I wonder if someone can help me. The posts I have read about clearance in the past have refered to a number like .065 for instance. now my readings are .61 mm. Am I really that far off? A whole decimal place? Are the tolerences they are talking about that small? I changed the scale to SAE and that made even less sense. Or is the scale something different? I am missing something can someone help out?
 
Feeling very foolish

OK that changes things alot. I'm at .024. bad,bad,bad. I just didn't think about the measurement changing to empirical. So maybe this explains a part of why the 5 gaskets to get clearance. If am at .024 now more shims would get me up there to .055 or greater. But why is that necessary? what was done to require the greater space (gaskets)?
 
So is this a poor mans port job? do they remove the bottom gasket, or remove a layer of it? could that be why it's necessary to make up the difference at the top?
 
There was 5 layers of head gasket with the stock 1 pc cylinder head correct?
Assuming stock pistons then the cylinders could have been milled down or the head as well. Base gasket may have been thinned also.
If the base gasket is an oem one it is a 1pc. In order to change one jug it would require aftermarket base gaskets using 3 individual ones. Then you could remove a layer for whatever reason.
 
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Yes that is correct. The stock head had 5 layers of gasket material under it. So if I am hearing you right the previous owner may have cut the cylinders down. I would assume to raise compression? but cut too much,so shimmed up to get the right squish. Is that about right? If the jugs are different heights does that mean that it was cut too far? Or maybe from a different machine? So next question, can you purchase layered aftermarket base gaskets? So that I can adjust the height of the center cylinder? And if so any sugguestions where? Thanks for all the help. I obviously need it.
 
I would pull the jugs as well. Get a good look if it was ported or not and good look at pistons and rings. If nothing else you should be able to tell if base gaskets are they same, if they are it would suggest some one had that jug decked. Entirely possible some one had all 3 jugs decked, parted sled out. Sold 1 jug to previous owner and he didnt notice til he was putting head on like you did. Crazier things have happened. I wish I had $1 for every time I was working on something and the thaught "what the hell were they thinking?" while trying to make it "right".
 
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Could be as simple a aftermarket (thicker) base gaskets on outside cylinders and OEM on center. Tear them off and see. If the center is cut down you might be further ahead to have other 2 cut to match or pick up a used jug. I picked up a used jug/piston (00 sxr 700 same motor) off flea bay for $80, was actually as nicer or nicer than the 2 good ones on my sled.
 
So possibly a new jug? It is ported, so now I need to get a matching port job. I guess I need to pull the jugs and look at what I am dealing with. Maybe it's a gasket. HMMMM
 
read over the post and you have been given good advice,as the base gasket is either been cut and used,as the stock base gasket is 1pc metal. More then likely the cylinders have been decked, its possible you have a mismatch cylinder in there to get back up and running and the sled was then sold to you hence the funky headgasket layers. They likely couldnt do the required headwork on the 1pc head, as it takes a "big lathe" to get the swing needed or unless you have the special cutters made for the mill like i have to redo the chambers.

Be best to remove all 3 cylinders and measure the cylinder heigth, and then see what you have for base gasket, should be all 1 pc, if its not someones been in there messing around.

check those things and report back. I would also check and see if the cylinders all have roughly the same dimensions on the ports so your not dealing with a ported center and stock outers or whatever the combo may be.
 
plan of action

Well it looks like I am going to get a lot more intimate with my engine. I have (and always will) more questions. I haven't heard the term "Decked before" from it's usage I assume it means to shave off the top? or bottom? of a jug? Again I don't know, I am asking. I would assume that this is done to increase conpression, and maybe? to step up the port timing?(assuming it was done on the bottom. Is this a common thing done to gain performance? I am thinking I will tear down the engine to get out the jugs. I do not know if I have the proper measuring equiptment to determine if these jugs are OK. I read in my manual "my bible" about a device that measures the inside dimensions of the cylinder walls, and can do so all the way down the cylinder. I personally only own a set of digital calipers right now. I do not know if that will be sufficient. Maybe I can rent. Or get a local machine/motor shop to gauge it for me. If they are cheaper now maybe buy? Anyway back on task. I am thinking that The machinist who did this over cut the center jug. If the jugs are close in the porting, and the dimensions inside are within tolerence, What is the problem with stacking gaskets? I know, I know this is not ideal. However, This machine has run well for two years. I do not know what I will find (obviously) when I pull the jugs, but I am just getting a picture, and looking at options. Thanks for the advice and patients.
 
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question for MRviper700

You mentioned the lacking the equipment to do the head properly. I am trying to follow your line of thought. First I am not,not a mechanic. This machine is the first thing I have worked on. So am I to gather that this decking was only the first step, and should have been followed with a re-working of the head? Is that correct? I read as much as I can on this and other sites, but do not know all the terminology, and have no real world experience with the processes. I read a few threads about "shaving" the head. This seems to be an art form. The sculpting of the combustion chamber and angles within. From what has been said you are one of the few artists who do this. But my question and belief would be that the peak head would be a step in the right direction. No? Or did I miss something in this? Thanks :2strokes:
 
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