worn exhaust valves

[snootbiscuit]

hey folks. rec. had to rebuild my 08 poo 700 cfi. w/ 6100 miles, after doing some reading, here and on hcs, I see some reports of valves hitting pistons. after further inspection, mine were getting close! I inspected the shoulder, on the guillatine,and it sure appeared to be worn. I ordered new ones. when I got new ones, I measured the shoulders w/ digital venier. the new ones measured just under .100", the used ones were under .070"!! I read where guys were grinding off, approx. .025 ,the front edge. I would have been ok w/ that, but the thing I didnt like was=if the integrity of the metal has been compromised, then where is the material going from here on out, into the cylinder!! also measured my 07 600 cfi w/ 2000 miles and those were over .100"!! I recorded all readings and I will be checking mine during cleanings here on out. just a last thought 4 some of you "metal gurus" , do u think the hardness of the shoulder is compromised over time, because of the "light pounding" on the shoulder from bottoming against stop in cylinders? sorry 4 the long post, just wanted to get this out to u guys,maybe save an engine or two!!

 

[G]

Unfamiliar with CFI engine but have a trick that might help you. On my old AC 800 with exhaust valves clearance could be an issue over time. On that particular motor the problem was solved by shimming the whole exhaust valve mechanism away from the engine with a small .010 or so shim. I don't remember the exact width but it was enough to keep things apart. This is a better option than grinding away on the valve itself. Again I can't picture your CFI but I would sure think something like this would work for you.

 

[srt20]

I have been following this too. I have 6800 miles on mine, and have not checked them yet. But I remember reading that whoever was having this problem, that the shim deal would not work for some reason. I cant recall exactly why it wouldnt work, but better check into it before just shimming it. Grinding will not compromise the metal, it just doesnt get hot enough. The incylinder temps are much higher than grinding temps will ever be.

 

[snootbiscuit]

yo srt, I wasnt so concerned about the metal integrity, at the leading edge,where they would get "ground", it was more so in the area of the "shoulder" that's part of the shaft. if you get yours out and look at this area, I'll bet yours are shiny and look worn.like I said at beginning of thread, I measured both old and new guillatines,and there's quite a diff.! about the "integrity of the metal" question, I know metal can get fatigued and it can also "work harden" with a tapping or pounding effect,like what this shoulder or stop is encountering over time?? sorry if I am not explaining properly

 

[polarisfreak46]

I know a few teams that race in the MIRA series and the Sault 500 and they use shims. They say it might add a few HP. One team is the MIRA champions last year so I would trust it. the shims are ruffly 3/16 of and inch thick. I havent got around makeing any for my sled yet but I'm going to.

 

[snootbiscuit]

yo srt20, what does yours idle at when warm? mine is 1800,manual says 1700. I ordered the tps harness and just went thru the setup,starting with baseline setting. all specs were spot on before checking and after. just curious more than anything! and I checked boots really well at rebuild and today (200 miles later)

 

[srt20]

I think mine idles at 1700 give or take 50 when warm. I dont check rpms much, I listen more. I really only check WOT rpms because of the clutching I do. I have never checked TPS cuz sled has ran exactly the same since new. Maybe I should have when it was new??

I will pull my valves this week and take a look. They are prolly in need of a cleaning anyway, cuz I dont use full synthetic oil. I got 1600 miles since I cleaned them at the beginning of the season.

 

[snootbiscuit]

srt20, thanks for the replies! sure is nice to have another sled to compare to. b4 u yank valves, curious what kind of compression readings ur gettin?if u ever want to check ur settings let me know,I'd be happy to help. I have polaris man. and polaris harness from spx.nice mileage so far!u ever want to hook up, I'm in mukwonago area

 

[srt20]

I dont know if I will get around to checking my valves now. I made a mistake today and stopped in at the local Ski-doo dealer.........