Motor Breakdown

[who_gives_a6]

If anyone followed my previous topic, I have torn down a little more to investigate why the quad would not start. It appears that timing was obviously off a bit. Also take a look at the piston/rings and tell me if I'm missing something. Shouldn't there be 3 rings? There's only 2. One in the top grove and then the bottom is the oil rings I take it. There's a center groove that looks like it's for a ring as well but none there. The top ring has the gap slightly to the right of wrist pin on exhaust side. Haven't taken the piston off yet but gives you an idea.

The cylinder has some slight scarring it looks like on both sides near the wrist pin holes and there looks like rubbing on the walls on both the intake and exhaust sides. Each is in the pictures. The piston picture shows where the valves were tapping the piston. You can't feel it but it's obvious to see. You can also see it on the pic of the valves.

The previous owner finally responded to me and gave me the receipt copy for rebuild. Was done by Blackwidow ATV in Utah. Has a CP 450 piston and 97mm bored cylinder, new cams, top end was fully redone with all new parts and head was ported, 5th gear modification, new clutch, all new bearings/seals all over, brand new crank from ATK with LTZ bearing and balanced, and some more odds/ends it appears. A bunch of new bolts and such too. The case also appears to have been damaged where the drain bolt for tranny goes and then welded, retapped, and a new bolt installed.

So any opinions where to go about this now or the next step? I want to ride this thing. Something has to be wrong here. I also noticed there seems to be a decent bit of movement in the crank but being a brand new engine with build receipts and such, must be right?

[who_gives_a6]

More.

[2000ex]

Looks like the timing was off causing that issue. The only other thing it could be would be a slightly bent rod causing the piston to valve contact you see there. If this motor was never run and was built by blackwidow, this repair should be on their dime. Piston and intake valves should be replaced as well as the rod checked for straightness.

[cannondale27]

There was alot of hrs on that piston so it was obviously at least piston was run.Its kind of odd to see the valves hit that hard.I would suspect crank bearing is gone or someone had it apart and screwed up later on.

[MX Quad Dad]

nobody said anything about the missing ring. I've never heard of anyone leaving it out. and I always try to stay a little farther away from the centerline of the wristpin.

[2000ex]

There are only 2 rings on a CP

[MX Quad Dad]

QUOTE (2000ex @ Dec 16 2010, 10:41 AM) <{POST_SNAPBACK}>

There are only 2 rings on a CP

But it does look like there is a groove between the two.

[MX Quad Dad]

I don't know how well you know the guy you bought it from. If it were mine, I would go through everything since it is apart. I don't know Brad other than talking on the phone a couple years ago and whats written on these sites and I have a hard time believeing he would let something like this leave his shop as an assembled engine ready to run. but regaurdless its was not done right. so the crank should be tore down to at least check for the Z bearing and balance. piston does show wear so it needs to be mic'ed but I don't like the idea that the valves were tap dancing on top of it, so I would put new anyway or if you ship any parts out to have work done by one of the experts here, send the piston and have them look it over for you. The head should be checked for sticky buckets so I would send it out and have it checked over, but I would figure on new valves.

if you are going to just putt around with it you might get away with cutting cost. but if thats your plan you got the wrong quad

I know this sound like a lot, but you can scrap out a lot of good parts real quick and be out the money you have already spent, going to spend and time, and still have a quad that won't run. you are in the right place though. with some pics and maybe a few measurement some of the guru's here may be able to save you a few bucks safely.

[wistech]

Hitting all 4 valves makes me suspect a head shaved down to far.. Incorrect cam timing should only smack the intakes or exhausts but not both.(most of the time) Could you mic the head from the top machined part to the bottom and post up the dimension. If the valves are not bent that would also indicat the piston was contacting closed valves. I doubt the rod would be bent or the piston dmaged unless they wrenched it over with a big bar and cracked the piston. Id dye it for cracks to be sure.

[who_gives_a6]

As mentioned in previous post: when I got it on the bench still together with side cover off, the thing was real hard to turn over when it got to TDC. When I took off cams and such and just redid the timing by instructions on this site to be sure, it became real easy and smooth to turn over. Felt like very little resistance and no binding feeling anymore. So possibly it was just timing out of wack making all four valves hit? What I noticed when turning it was that when the exhausts would go down when piston was at top of cylinder. Then when it'd go down and come back up the intakes would open and go down. So basically every time the piston came up a set of valves appeared to be hitting it.

So you all think the piston was run alot? Previous owner said he tried to get it to fire a ton of times and I tried quite a few times switching out electrical parts and such, but has never ran. There's no carbon on anything anywhere. Lots of assembly lube on parts and loctite on bolts, so looks like they knew what they were doing when building to me. Just maybe fudged up the timing. So even though you can't feel the spots where it's rubbing on valves and piston, are you all as a whole agreed that the valves are toast and possibly piston too?

I'll have to try and do some measurements this weekend. I want this thing to be a runner, so will have to do what it takes I guess. More money to the beast. Don't exactly have a lot of spare cash to spend to get this done right though.

Edit: There's some info on the paperwork that also says sticky exhaust bucket machined. It appears that literally every piece of this engine was brand new or fixed during the build. I'm more worried about the piston now becuase I know the guy had wrenched it over with a large 1/2" ratchet connected to it, per his admittance. What would you use to test piston for cracks? I'll take it off tonight and give it a lookover or test it.