[scsmith42]

I'm in the process of rebuilding the top end on my 06 Ranger 700 EFI 6 x 6. This project has actually been in the works for about 2 years; I've managed to keep postponing it until the engine finally quit working last month.

The cylinder walls wore extensively at the top of one of cylinders and blowby was causing extreme oil consumption and plug fouling on the other cylinder (presumably due to the blow-by from cylinder 1 pushing oil past the rings into the chamber on cylinder 2. The compression finally got so bad on the first cylinder that it would not run.

It is an unusual cylinder wear pattern that I have never seen before. Of the portion of the cylinder where the rings ride, the top 3/8" was extensively gouged and worn (about .030 - .040 of wear) over about 1/2 of the cylinder. The rings that corresponded with this portion of the cylinder were extremely worn as well. The resulted in a significant loss of compression only when the cylinder was at TDC and maximum pressure.

The problem originally showed up when the first fuel pump failed when the Ranger was about a year old. Subsequently the plastic intake manifold cracked on the bottom (due to seat pressure from above - pre the metal bar fix that Polaris came out with). My original deduction was that the cracked intake caused the mixture to lean out and thus scoring the cylinder, but when it was disassembled the piston skirts and cylinder walls look fine - no scoring. The only abnormality is the wear in the cylinder at the top. Strange.....

Chris Ball helped me out a couple of years ago with obtaining replacement OEM pistons, gaskets and a cylinder kit, but when I tore it down yesterday I noticed that the valves have significant wear where they meet the seat and if I grind the original valves there will be sharp edges - not a good thing.

I was really surprised by the amount of wear on the valves considering that the ranger only has 810 hours on it. Both intake valves are worn about the same; the exhaust valves are not worn as much as the intakes. The guides are tight (which is usually what wears before the valve seating surfaces). As I recall, typically wear on the valve face is due to either excessive spring pressure or low lubricity in the fuel.

There have probably been 50 times when the engine has been operated at redline for 4 - 5 minutes at at time (running 3 miles down the road to a local gas station), but other than that it encounters a lot of start - stop work for 1 -2 minutes running across the farm or back and forth from the house to the shop.

Has anybody else encountered valve wear like this? I also noticed that Polaris indicated that they had superseded the original valves with new ones so perhaps the original ones were too soft....

Thoughts appreciated. Thanks much.

Scott

 

[rowe doo]

Look's like a lean mixture problem to me with soft valve's

 

[carnivore]

It looks as if you had some dirt ingestion to me. The cracked intake is the likely cause.

 

[nFLOW]

Yes, l agree with Carnivore, looks like some dirt has made its way in the engine. The plating is gone at the top of your cylinder. Once a little bit of debris gets into your engine, it acts like sandpaper to your cylinder walls and valves. If you have any questions, I will be glad to help. www.nflowmotorsports.com

 

[scsmith42]

Guys, thanks for the feedback; that makes sense re the dirt ingestion because I live on a farm with dirt roads.

I ordered new valves last week and assembled the heads today. Valve seats are not rounded, and the seat width is coming out at around .050 - .060 for the intakes and .080 or so for the exhaust. Outer seat widths are around .015 per side in from the outside of the valve so I think that I'm good to go with respect to the heads. These dimensions are pretty much in line with the specs that I used 30 years ago when I was building race engines. Although the old seals looked good I went with new.

I must say that I am impressed with the quality and engineering of everything that I've seen inside the engine. Having the intake crack due to the Ranger seat riding on it was a real disappointment (as was the lack of warranty on what should have been acknowledged as a design flaw), but from what I've seen inside the engine is well designed and manufactured. Roller rockers, brass exhaust valves, tulip intake valves, precision valve seat shaping - this was all cutting edge racing technology "back in the day" and it's nice to see it used by Polaris. Other than the piston/cylinder wear everything else looks in great shape.

Re the new piston and cylinders, ring gaps are within spec, and I am ready to start the reassembly in chassis. One question - I'm most familiar with wrist pin retainers that utilize internal snap ring pliers for removal and installation. Are there any tips for installing the wire style that Polaris uses? I don't want to over-compress them so that they lose tension, and they are a pain to compress!

Thanks much.

Scott

 

[POS POLARIS]

scott,

Best thing I've found to use is a strait O ring pick.

there's an indentation on the piston so that once 80% of the snap ring is in you can use the pick and pry in that notch to get that last bit in. I've over tensioned the clips before, so I always save my old one's just in case I wreck one of the new ones.

They are a pain in the butt. good luck

 

[scsmith42]

Yes, l agree with Carnivore, looks like some dirt has made its way in the engine. The plating is gone at the top of your cylinder. Once a little bit of debris gets into your engine, it acts like sandpaper to your cylinder walls and valves. If you have any questions, I will be glad to help. www.nflowmotorsports.com

Thanks much for your kind offer. It's nice to see a manufacturer from Evansville here; I used to live in Newburgh and still have close friends out on old Yankeetown Road near Alcoa.

Would you like to have my old cylinder? I have no use for it and don't mind sending it your way.

Scott

 

[scsmith42]

scott,

Best thing I've found to use is a strait O ring pick.

there's an indentation on the piston so that once 80% of the snap ring is in you can use the pick and pry in that notch to get that last bit in. I've over tensioned the clips before, so I always save my old one's just in case I wreck one of the new ones.

They are a pain in the butt. good luck

Good advice - thanks much. Fortunately I have a couple of picks on hand so I'll give that a try.

 

[POS POLARIS]

forgot to mention, its best IMO if you install the pistons into the new jug first, and then try and slip the pistons over the rods and get the two clips put on. I'm not gonna lie, it's not easy standing on your head while trying to fiddle with those clips and a O ring pick without somebody getting hurt. lol

Here's a video I did on my last top end rebuild. unfortunately I didn't get as much on film as I'd have liked. it might be of some help to you.

 

[scsmith42]

Adam, thanks for the info and video. My thinking is similar to yours regarding installing the pistons in the cylinders first. It would be extremely difficult to insert the pistons into the cylinders from the bottom w/o damaging the rings. Mine went in from the top just fine.

I'm headed over to the barn to resume the assembly. Thanks again to all for the advice.

Scott

 

[scsmith42]

The installation of the circlips went a lot easier in the chassis than on the bench. Top end is back together. I'd like to replace the gasket from the intake to the head but it does not appear that Polaris sells one separately (does not show up in the parts diagram - only the entire intake assembly). Should have it running on Tuesday depending upon how Monday's work projects turn out.

 

[POS POLARIS]

Scott,

there is no intake gasket between the boot and the head. there is a slightly raised rubber rib that runs around the front of the boot. although it is very hard to see once it's been taken off after being on the engine a long time.

If I re-use the boot, I smear a thin film of silicone on the face of the boot before I put it back on. Call it peace of mind. if you do this, use a very small amount, you don't want it protruding into the intake once the boot is tightened down. I perfer permatex ultra grey rigid silicone, but anything will work as long as it's automotive grade.

Now would be a good time to clean out the bore and butterfly of the throttle body as well as the t-map sensor before you get it all back together.

 

[scsmith42]

Scott,

there is no intake gasket between the boot and the head. there is a slightly raised rubber rib that runs around the front of the boot. although it is very hard to see once it's been taken off after being on the engine a long time.

If I re-use the boot, I smear a thin film of silicone on the face of the boot before I put it back on. Call it peace of mind. if you do this, use a very small amount, you don't want it protruding into the intake once the boot is tightened down. I perfer permatex ultra grey rigid silicone, but anything will work as long as it's automotive grade.

Now would be a good time to clean out the bore and butterfly of the throttle body as well as the t-map sensor before you get it all back together.

Good advice - thx. I've also totally cleaned the air box and feed pipes to the throttle body to make sure that there is no dirt present (there wasn't).

It's all back together but I still need to weld a piece of the square tubing seat chassis back in place. We had to remove a 10" wide section in the middle in order to get the top end apart. I also want to visually inspect the spray pattern from the fuel injectors before reinstalling them to ascertain if the pattern is similar on both.

Also need to do an oil and filter change.