motor rebuild crash course

[bbender85]

so i didn't see a sticky, and weeded through some posts to get an idea, but here is exactly what i am after:

quad supposedly has a 416 kit, but smokes/burns oil something fierce (a quart a day). so i want to do an 11:1 426. ebay has a Wiseco piston kit and Cometic topend gasket kit combo available.

1. what else do i need?

2. valves: how do i check them to see if the seals need done? if they do, do they need pressed in? any machine/special work? will they need timed (if i do OR don't replace them)? anything else valve-related?

3. obviosuly the cylinder needs bored; is it supposed to be right at 88.00mm?

4. timing chain: replace it while its apart? if so, seems like i've read of using an HD chain from another honda motor? does this require additional dis-assembly?

5. planning a stage 1 hotcam: anything special here? seals/etc. need to be pressed on w/ special equipment?

6. I have a knock, sounds like mid cylinder; is this likely the wrist pin? or am i look at crank work too?

7. what did i overlook?



i am very mechanically inclined, so i am not afraid to dig in... but some guidelines would be great, as i've never been in one of these before.

does someone have a writeup somewhere? perhaps a pictorial?


thanks everyone.

[jeepthing07]

Originally posted by bbender85
so i didn't see a sticky, and weeded through some posts to get an idea, but here is exactly what i am after:

quad supposedly has a 416 kit, but smokes/burns oil something fierce (a quart a day). so i want to do an 11:1 426. ebay has a Wiseco piston kit and Cometic topend gasket kit combo available.

1. what else do i need?

2. valves: how do i check them to see if the seals need done? if they do, do they need pressed in? any machine/special work? will they need timed (if i do OR don't replace them)? anything else valve-related?

3. obviosuly the cylinder needs bored; is it supposed to be right at 88.00mm?

4. timing chain: replace it while its apart? if so, seems like i've read of using an HD chain from another honda motor? does this require additional dis-assembly?

5. planning a stage 1 hotcam: anything special here? seals/etc. need to be pressed on w/ special equipment?

6. I have a knock, sounds like mid cylinder; is this likely the wrist pin? or am i look at crank work too?

7. what did i overlook?



i am very mechanically inclined, so i am not afraid to dig in... but some guidelines would be great, as i've never been in one of these before.

does someone have a writeup somewhere? perhaps a pictorial?


thanks everyone.


I am going through this myself on a 400ex i bought i havent even got to ride yet. You might need a new connecting rod. when i tore my motor down it ran fine but the wrist pin and rod were galled and it seems to be a problem on the 400ex from what i have read. so i upgraded to a hotrods crank and it has a bushing in the end of the rod and its not tapered like the stock one. it looks like it will hold up much better.

I don't know if this is the correct way to check valves but i just filled my intake then exhaust ports up with water to see if they leaked (they diden't) i'm still going to lap them a little before i put it back together.

You should take the piston in with the jug and they will fit the new piston.

I read that the CRF450 timing chain is HD and will replace the stock one and its only $30. and it takes no more disassembly

bearings slide right off the cam no special tools needed.

If its a wrist pin your looking at crank work.



You might want to install HD head studs while its apart.... And from what i have read Wiseco pistons suck. i have herd a lot of bad things about them. like oval pistons... I never had any experience with them but i have read enough to make me choose a JE or CP piston.

[Chino886]

here are my suggestions:

New valve seals
new valves
new gaskets
new cam chain - crf
valve job
port and polish

The cam bearings slide right off. You should not need to get anything pressed on or off unless crank needs to be replaced.

[hypersnyper6947]

Originally posted by bbender85
so i didn't see a sticky, and weeded through some posts to get an idea, but here is exactly what i am after:

quad supposedly has a 416 kit, but smokes/burns oil something fierce (a quart a day). so i want to do an 11:1 426. ebay has a Wiseco piston kit and Cometic topend gasket kit combo available.

1. what else do i need?

2. valves: how do i check them to see if the seals need done? if they do, do they need pressed in? any machine/special work? will they need timed (if i do OR don't replace them)? anything else valve-related?

3. obviosuly the cylinder needs bored; is it supposed to be right at 88.00mm?

4. timing chain: replace it while its apart? if so, seems like i've read of using an HD chain from another honda motor? does this require additional dis-assembly?

5. planning a stage 1 hotcam: anything special here? seals/etc. need to be pressed on w/ special equipment?

6. I have a knock, sounds like mid cylinder; is this likely the wrist pin? or am i look at crank work too?

7. what did i overlook?



i am very mechanically inclined, so i am not afraid to dig in... but some guidelines would be great, as i've never been in one of these before.

does someone have a writeup somewhere? perhaps a pictorial?


thanks everyone.

1. That should be all you need as long as it comes with rings wrist pin etc.. I would send you cylinder to gt thunder with you piston and have them bore, hone and match it to the piston, at the same time i would have them install your HD headstuds. Put them in cause i assume you are going to up the compression a little bit to make up for that cam.

2. In my clymers manual it says to fill the the intake and exhaust valves with carosean to make sure they dont leak. If you need to do your valves get a craftsman c clamp style valve spring compressor ($20) this will make getting the valves out and in a snap.

3. Not sure i know my 440 is a 89mm ???

4. Gt thunder now has a HD timing chain they offer buy it and have them through it in the box when they ship your cylinder back to you. I think you will have everything you need to do this already dis-assembeled.

5. Everything for the cam installation is easy just make sure engine is at TDC and lobes on the cam are pointing down. Also you hash marks are level with the cylinder.

6. You will need feeler gauges for your valve adjustments, use these to test your crank/rod to make sure everything is still good to go. Pick up a clymers manual it will help a lot Pics galore and specs.

7. Remove decompression valve for cam, i would also heli coil all my bolt holes that hold on my valve cover, also your oil filter cover bolt holes. They all strip and it sucks.

As far as a pictorial about this pick up the clymers it will have a pic for everything and will help a lot. I got mine on ebay like $28 shipped.

I think i got almost everything im sure if i missed anythings someone else will come along and fix it.

[bbender85]

thanks for all the responses so far, great answers.


- resleeve; what does changing the sleeve consist of, workwise? machine shop work? i ask because i can get a 440 kit with a new sleeve for $20 more than the 426, which i think would be less than the cost of having my sleeve bored to fit the 426 piston; any insight on this? on that note, does the sleeve have to be removed from the cylinder to be bored anyways? if that's the case then i guess that answers this whole question.

- more on the valvetrain; in your experiences, what has NEEDED to be changed? i am not looking to half-*** this rebuild, but keeping cost to a minimum is key. this not being my main hobby, i don't have the funds to throw at it, or the desire for ultimate performance... just dependability.


thanks again, and please excuse my ignorance. :D

[dustin_j]

First off, my advice is to skip the stage 1 hotcam and go stage 2. I assume you're thinking stage 1 because you want more low end, but I've got a 406 with a stage 2 and my brother has a 426 with a stage 2. Both have much more low end than stock (his killing mine) and rev out much better.

The new sleeve needs to be installed by a machinist. The old sleeve is pressed out, the cylinder is machined to fit the new sleeve, and the new sleeve is pressed in.

Get a repair/service manual! It will answer many of your questions and allow you to measure components until your heart is content:D . I just rebuilt my 99 (I got it last fall and it still had a completely stock motor :eek2: ) and it needed new intake valves and I got a 3 angle valve job on them and the stock exhaust valves.

C&D Racing (site sponsor) did all my work and has very competitive prices. Good luck!

[hypersnyper6947]

if you bore to a 426 it will prob be cheaper, if you do the 440 they will have to press out your old sleeve, bore your actual cylinder to fit your 440 sleeve, then put in the new sleeve, then hone it and match it to your piston, where with the 426 they just bore the sleeve that is already in your cylinder and match it. I also agree go to the stage 2. like i said before just send your cylinder to gt thunder for the bore studs and HD chain.

[bbender85]

good call. ok so i ordered a 426 kit this morning. now i just need to find a used hotcam and a slip-on. thanks again everyone... there's a good chance i'll be back with more questions. :D

[hypersnyper6947]

^
bring on the questions i just went through all this and im happy to help