Top End Maintenance

[Rohr397]

Okay guys so as recommended by the one and only 01boneless

I am going to replace my piston rings and valve seats, I don't know what condition they're in but they've been in there for quite awhile and I do notice a little blue smoke. Luckily my oil level wasn't dropping at all, so I doubt I was burning through crazy amounts of oil.

For the piston rings, I am thinking about going with OEM. I want to go low budget on this without doing something cheap, and obviously OEM is pretty good quality.

As far as valve seats go I am thinking about doing something along the same lines, affordable but good quality. However, I have heard that there are high quality aftermarket seats for cheap as well.

Now for the biggest problem of all. I really trust my dealership and they're very friendly. On the brightside the parts counter people practically give me parts since I am in there so much. The downside is the mechanic there charges an arm and a leg. In order to have the work professionally done I have to spend an entire paycheck (about $300, not bad for a first job though). So I want to do this myself instead since that money needs to go towards my gas hogging truck. I've never done much with top ends and I don't have a clue what I am doing. All I've got is the basic owners manual that actually came from my mom's 03 Ex and after trying to follow the manual for my 04 450r I have the feeling it won't be too helpful. How hard would this be for a beginner to do with no outside help? What does it take to do this?

Sorry for the long thread. I know most of the mechanics of quads and all but I have never owned a quad long enough to need to do a whole lot of top end work, as I am sure boneless could tell you after being subscribed to me on YouTube for awhile :rolleyes: . Just the basics and all the chassis setup.

[05DodgeDakota]

What do you mean replace the valve seats? I'm thinking you meant seals? Anyways I just did mine, and the disassembly/reassembly wasn't bad, but you gotta have a machine shop hone the cylinder and have them measure the cylinder to piston clearance to make sure you can get away with just new rings and not bore + new larger piston. I would also have them disassemble the head and press in the valve seals and if nessisary, recut the valve seats.

[01boneless]

smoke on start up is valves seals smoke on start up and heavy acceleration is piston rings. you can do it its not hard but you do need a manual! and your meaning seals. now you have to remove the valves to install the seals witch isent hard you just need a spring compressor. then once you put them back in you will need to relap the valves (grind) you will need lapping compound and a simple hand drill . i will explain later just how to do it as its not hard. piston rings is a great idea to insurre a long race season on you quad. NOW you may get it tore down and find the bore being wore (seems to always go that way for me). no biggie just nned to have it bored to a 402cc . and buy new piston witch can be had cheap from wiseco. make sure when you instal rings to stagger the end gaps on the piston and grind the gaps to fit NOTE(if the new rings gaps measure to big when recived the bore is bad and needs bored) GOOD luck not hard at all but you will need a good torqe wrench!. ohh and thank you i am one of a kind arnt I :devil:

[Rohr397]

Why is that? I've always heard that you can just replace the rings. Most the topend is brand new minus the piston. My 400 originally had a full 440 kit on it and before they sold the quad they took it off and put the stock top end back on it, so it doesn't have too many hours of use on it. I don't even know if the piston rings need to be replaced or not to be honest. I was leaning towards valve seals (sorry for the mishap, 1am does that to you) but thought Id go ahead and freshen everything up. If this is going to be really expensive then I don't know what to do. Not to mention there's no machine shops around here, just a couple factory dealerships that charge an arm and a leg.

[01boneless]

dude anytime you tear down a quad you MUST check the cylinder clearance! im not saying its bad im not saying it isent tear it down and see its not real costly even if it is. if it dosent have to many hours on it id say new rings and valve seals should fix you up.

[Rohr397]

Okay so how would I do that, and what tools would I need? I can probably get the tools for free :P

[01boneless]

you will need baskic tools . then feeler gauges,torqe wrench,spring compressor bout it off the top of my head good luck only torqe the valve cover bolts to 7ftlbs they strip out real easy!

[Rohr397]

Okay haha I better get a torque wrench. I've been lazy this whole time using nothing but my trusty T-Handle lol.

[01boneless]

sketchy:eek2: lol its not fun fixing a striped thread hole lol

[Rohr397]

Hahaha I know right?? Luckily I've never stripped anything! I start everything by hand then sinch it down snug, not professional but I've never had a problem! Lol I take that back I broke the rotator clamp bolt on my Yfz from over tightening, so I've messed up once. Not a bad track record though!

[CJM]

What you need to do is check the piston ring clearances. To do this you remove the topend and the piston. Then take the rings, take one and put it in the cylinder use the top of the piston to push it down evenly then measure it with a feeler gauge by sticking the gauge i nbetween the gap in the rings, the manual will have the ring clearance. If the clearance is to great your bores worn out.

Example: I took mine apart to re-ring it. I had the rings and all and found that my clearance was supposed to be .14mm and .17mm for the 1st and second rings. I could EASILY fit .22mm and .25mm. I said eh...thats alot Im going nuts somethings off, I must be doing something wrong???? After triple checking and asking others here I concluded the bore was shot-specially after I took my caliper and checked it (I wish i had something more accurate but good inside micrometers are very $$$) So I said eff it Ill buy a new piston and bore it. previously the piston-rings and all went in there WAY easy. Bored I checked the ring gap-wasnt truly ideal as I had wanted to close-remember they expand with heat. So I put it together and could BARELY even all lubed up get the piston in there-I had done the right thing and bored it at this point.

The topend job isnt hard, bit time consuming but not hard. Be aware you will need to retime everything properly, put the piston rings on the piston right and assemble/take apart everything. If you have never done this before I suggest you read up on it and take your time while you do it. A friend is also helpful!@

[01boneless]

i done the same same it smoked tore it down without checking the ring gaps put it back together tore it down again checked them and you could drive a truck between em