SRX engine after 11,000 miles

D

dockter71

New member
Joined
Oct 29, 2003
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56
Location
Maple Grove, Mn.
I did a Hot compression check on Sat. and the PTO was at 100, 105, 105 mag side. Pretty sad actually. But for 11,000 miles what do you expect. I had the sled all ready to go for the season, and then I find myself tearing the motor down. I ordered the .031 base gasket from Maxximum, the complete ring set through Ronnies, and my heads are being milled .025" tommorrow at a local machine shop. Also gonna replace the tired reed petals. I really have been going back and forth on whether I should port using the race logic templates or just do the lift and shave deal. Also I have really been considering aftermarket reeds, but have heard it doesn't pay for itself. So I have decided to just do the lift and shave method and keep it simple. When I got the cylinders apart, everything looked good on all cylinders except for one small area between the main exhaust port and the smaller port just to the right of the exhaust port on the PTO jug. This area (about a 1/2 inch wide) had scoring on the piston and the cylinder, throughout the entire travel of the piston along the piston and cylinder wall. There was also some extremely minute marks on the rings in the affected area. Other than that all the honing cross hatches was still there and I could not feel any wear on the thrust faces of the cylinder wall at the top of the stroke. Found quite a bit of varnish and blow-by below the rings on the exhaust side and also down around to the piston pins. All pistons looked new, without any real visiable signs of wear to any surfaces. I did a quick diameter measurement using my digital calipers, .39" up on the on the skirts per the service manual and I kept getting numbers around the 2.7050 on all pistons, which is less than the minimum size called out in the manual. I'm gonna have my buddy at the machine shop get me detailed measurements on the jugs and pistons. I imagine the piston-to-cylinder dimension is gonna be the more important one. Also the reeds were still tight up against the cages. Hopefully I'll have it back together over the weekend.
 

I ported my 00 useing the Race logic templates.They was easy to do.Just waiting on snow to see how it works out.Also cut the heads .010 and reringed it.If you look on Ebay Racelogic runs a few actions on there.They have one where they will port your cylinders for you and cut the heads for like $370.Not bad of a deal really.
 
SRX 11,000 mile - update

I just got word back about the Cylinders and pistons. Well the pistons were well below the Spec minimum, so replacement is a must and the cylinder showed little to no wear. The owner said what ever I was doing (oil, warm-up s, etc) to take care of the engine, that I shouldn't stop. He commented though that this was about as far as those piston would have went, before skirt failure due the excessive rocking, or major scoring from the blow-by. As a result I was gonna replace pistons with wiseco pistons and replace the wrist pin bearings. A light hone and mill the heads 25 thou. So here is my questions / concerns. The machinist / owner said he thought the heads have been milled down before, and was concerned about taking .025" off the heads (even after I explained the thicker base gasket). He said he has done work on other yamahas and and hasn't seen a head that looks like this. Meaning some tell-tale sign of previous work. I told him I purchased the sled new and was standing there when they un-crated the sled, and didn't swap anything at that time. And then there is the question raised about the squish. What kind of variation are you seeing in the squish? What kind of squish is acceptable, and how is it measured? Could this have anything to do with the head on my 99SRX? Also Regarding the .031" thick gasket install and the .025 head shave, aren't I loosing compression (.006" worth) or i'm I missing something here. I went with the .025" because of not knowing the status of my gas I purchase in the backwoods. Should I forget the .031" cometic gasket and just go with three stock base gaskets instead?
 
After a little research I found on one of the many Yamy forums here , a good conversation about he variations being seen in the squish from various years.

http://www.totallyamaha.net/vbul2ph...f2fa399533afeac4646533db681e028&threadid=9267

Then after I took my smart pills, I realized how dumb my compression question was. By milling the head this reduces the head volume and thus increases the compression. The increase gasket thickness vs reduction of head thickness is not directly proportional.

So really the only question is how do I measure the Squish? I go and do some surfing for this. As you guys can see this engine work is all new to me. Any help is greatly apprciated. thanks.
 
No i didnt measure the squish before.I had Simons CPR cut them.He had me write down everything i did to the motor and what i wanted out of it when i sent the heads in.
 
Atlas, could you do me a favor? Take a piece of solder, about .060" diameter, and measure your squish? I'm VERY curious to see where it is. Have heard that stock there were some .070" and .060" motors. My bottom end with the cylinders and pistons of another sled and my stock heads measured .055" and the only thing that everyone seems to agree on is don't go below .050" for trail riding. I'm interested to see where yours ended up and how it runs.

Thanks,

Bigmax
 
I can measure them and post back later but they may not be the same as yours is.He cut the squish band on my heads cause the motor was ported.He said a stock motor didnt need the squish band cut just mill the heads.
 
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