stock bore high comp piston.

[casey_lamm]

Im looking for a high compression piston. Using stock bore. Most have a proven track record and leave the bike reliable...

Anyone have any ideas of brands to look for? Where to get them.

I have no complaints against Wiseco. Motosport.com

[casey_lamm]

is there a certain threshold for compression where you start losing reliability.?


Originally posted by FoxHondaRider
I have no complaints against Wiseco. Motosport.com

[drew416ex]

I personally like JE or CP pistons. But I have also used wiseco and have never had a problem. Reliability isnt an issue with compression, but anything higher than 11:1 you will want to look into race gas. You maynot want to go with stock bore though unless it is a brand new never used cylinder. Even if it is in good shape the piston to cylinder clearance may be too much. The clearance should be about .002", but after honing it, it could be .004 or more which is pretty much considered worn out.

[casey_lamm]

i understand your point, but dont want to bore the cylinder.

11:1 is what im looking for I think

So what would you suggest . its an 07 with low hours on it...i assume the cylinder is in good shape, but haven't had it apart to know.


Originally posted by drew416ex
I personally like JE or CP pistons. But I have also used wiseco and have never had a problem. Reliability isnt an issue with compression, but anything higher than 11:1 you will want to look into race gas. You maynot want to go with stock bore though unless it is a brand new never used cylinder. Even if it is in good shape the piston to cylinder clearance may be too much. The clearance should be about .002", but after honing it, it could be .004 or more which is pretty much considered worn out.

[drew416ex]

If you dont want to run race gas, go with 11:1. You can run 93 octane wit it. As far as brand, any of those three i mentioned will be fine. I preffer the JE and CP because I am more of a hard core racer and the tolerances seem to be a little closer, but ive also used wiseco and never had a problem. If you are looking for more power, you wont tell much difference with just the piston. A little, but not much. You may want to look at a hotcam stage 2, but if you dont have the money, I know where you are coming from.

[casey_lamm]

i was doing hotcam stage 1 at the same time..


Originally posted by drew416ex
If you dont want to run race gas, go with 11:1. You can run 93 octane wit it. As far as brand, any of those three i mentioned will be fine. I preffer the JE and CP because I am more of a hard core racer and the tolerances seem to be a little closer, but ive also used wiseco and never had a problem. If you are looking for more power, you wont tell much difference with just the piston. A little, but not much. You may want to look at a hotcam stage 2, but if you dont have the money, I know where you are coming from.

[hornetgod13]

You are doing the exact same mods I'm currently getting ready to install. I have a Hotcams Stage 1 cam and Wiseco 11:1 high compression piston with stock bore be shipped to me right now. I just tore the motor down and I'm waiting for all the parts to arrive. I'm also replacing the valve seals and installing a Heavy Duty cam chain while I've got it torn apart.

[casey_lamm]

sounds good hornet. are you honeing your cylinder? Are you worried about clearance that was indicated above?


Which piston are you going with...im either going cs or wiesco (sp?)




Originally posted by hornetgod13
You are doing the exact same mods I'm currently getting ready to install. I have a Hotcams Stage 1 cam and Wiseco 11:1 high compression piston with stock bore be shipped to me right now. I just tore the motor down and I'm waiting for all the parts to arrive. I'm also replacing the valve seals and installing a Heavy Duty cam chain while I've got it torn apart.

[sc400ex_rider]

i did this same thing and it worked out great on a low hour machine. i also just put the first set of rear pads on at the same time. i replaced everthing at once, i lightly honed the cylinder just to break the glaze (like 10 passes thats it) or you can use a ball type glaze buster. new valve seals always. it runs great im doing the sparks keyway and lightened flywheel next.
http://i140.photobucket.com/albums/r20/starcraftier1/S4010415.jpg

[hornetgod13]

Originally posted by casey_lamm
sounds good hornet. are you honeing your cylinder? Are you worried about clearance that was indicated above?

Which piston are you going with...im either going cs or wiesco (sp?)

I'm taking the cylinder to a machine shop today to have it measured. The service limit on a stock bore is 85.10mm. I'll let you know what I find out. If it's with in limits, I'm just going to have it honed. If it's over the service limit, than I'm going to bore it to 85.50mm (402cc).
I ordered a Wiseco Hi-Comp 11:1 stock bore piston. I hope it still fits or I'll be re-ordering. Wish me luck.

[hornetgod13]

Just got back from the machine shop and this is what I found out. The cylinder is still with in limits (hi-end side). The limit is 85.10mm and it was tapered. Near the bottom it was 85.02mm, middle was 85.06mm and near the top it was 85.08mm. It also was slightly out of round and had a few small scratches that they weren't certain would hone out. Taking all that into consideration, I decided to bore it to 85.50mm (402cc) to give it a fresh start. Luckily, I was able to catch the piston seller prior to them shipping the stock bore piston out.
Does $75.00 sound like a decent price for boring and honing to .020 over? I might look around for a better price but, this shop is one of the best around. I have to wait until the new piston arrives prior to having it bored anyways.

[drew416ex]

[QUOTE]Originally posted by sc400ex_rider
[B]i did this same thing and it worked out great on a low hour machine. i also just put the first set of rear pads on at the same time. i replaced everthing at once, i lightly honed the cylinder just to break the glaze (like 10 passes thats it) or you can use a ball type glaze buster. new valve seals always. it runs great im doing the sparks keyway and lightened flywheel next.
[IMG]

Dont used the sparks key on the 11:1. It will cause the engine to run too hot. Its designed for stock compression.

[drew416ex]

Originally posted by hornetgod13
Just got back from the machine shop and this is what I found out. The cylinder is still with in limits (hi-end side). The limit is 85.10mm and it was tapered. Near the bottom it was 85.02mm, middle was 85.06mm and near the top it was 85.08mm. It also was slightly out of round and had a few small scratches that they weren't certain would hone out. Taking all that into consideration, I decided to bore it to 85.50mm (402cc) to give it a fresh start. Luckily, I was able to catch the piston seller prior to them shipping the stock bore piston out.
Does $75.00 sound like a decent price for boring and honing to .020 over? I might look around for a better price but, this shop is one of the best around. I have to wait until the new piston arrives prior to having it bored anyways.

$75 sounds kinda steep. Around here it only costs $40-$50.

[JOEX]

Originally posted by hornetgod13
Just got back from the machine shop and this is what I found out. The cylinder is still with in limits (hi-end side). The limit is 85.10mm and it was tapered. Near the bottom it was 85.02mm, middle was 85.06mm and near the top it was 85.08mm. It also was slightly out of round and had a few small scratches that they weren't certain would hone out. Taking all that into consideration, I decided to bore it to 85.50mm (402cc) to give it a fresh start. Luckily, I was able to catch the piston seller prior to them shipping the stock bore piston out.
Does $75.00 sound like a decent price for boring and honing to .020 over? I might look around for a better price but, this shop is one of the best around. I have to wait until the new piston arrives prior to having it bored anyways.
Does seem kinda high but you're in California so it may be reasonable. And if the shop is the best around it may be worth it.

Running the Sparks key with 11:1 may be possible with higher octane fuel.

[hornetgod13]

Originally posted by JOEX
Does seem kinda high but you're in California so it may be reasonable. And if the shop is the best around it may be worth it.

Running the Sparks key with 11:1 may be possible with higher octane fuel.

I'll call around and get some other quotes on the boring.

I e-mailed Curtis Sparks on the timing key issue. I might go back to a stock timing key for an added piece of mind anyways. I've read conflicting posts on the use of an advance timing key with aftermarket pistons.

[casey_lamm]

website says use only stock piston.



Originally posted by hornetgod13
I'll call around and get some other quotes on the boring.

I e-mailed Curtis Sparks on the timing key issue. I might go back to a stock timing key for an added piece of mind anyways. I've read conflicting posts on the use of an advance timing key with aftermarket pistons.

[hornetgod13]

Originally posted by casey_lamm
website says use only stock piston.

I'm already aware of that. I have read that it can stay installed on pistons smaller than 416. I'll just remove it to avoid any overheating issues and be done with it.

[casey_lamm]

what do I need to take the machine shop..what specs do I need to give them?

[hornetgod13]

The first thing you need to do is have the cylinder measured on the top, middle, and bottom every 90 degrees. The inside diameter should be no greater than 85.10mm (3.3468in) at any of the points measured as well as the out of round and taper should be no greater than 0.05mm (0.002in) . Remember if you hone it you might take a little off for that too. The honing should only take off the glaze so the new piston ring will break in properly.

[casey_lamm]

i guess ill ask a dumb question, if im going through this much already...taking it to a machine shop etc...why not just bore it?


Originally posted by hornetgod13
The first thing you need to do is have the cylinder measured on the top, middle, and bottom every 90 degrees. The inside diameter should be no greater than 85.10mm (3.3468in) at any of the points measured as well as the out of round and taper should be no greater than 0.05mm (0.002in) . Remember if you hone it you might take a little off for that too. The honing should only take off the glaze so the new piston ring will break in properly.

do you have to get the cylinder honed or anything when you just drop a new piston in?

[hornetgod13]

Originally posted by FoxHondaRider
do you have to get the cylinder honed or anything when you just drop a new piston in?

Yes, you need to hone the cylinder whenever you change pistons. It's done to ensure the new piston rings break in properly.

[hornetgod13]

Originally posted by casey_lamm
i guess ill ask a dumb question, if im going through this much already...taking it to a machine shop etc...why not just bore it?

You need to measure it to see what piston you might need. If you don't premeasure it than that's your call but, if you intend to bore it you MUST bring the new piston with you. The new piston packaging box may also list the piston specifications needed for the shop to bore it correctly.

[casey_lamm]

ah, good info...thank you..

im thinking 416... :)
Originally posted by hornetgod13
You need to measure it to see what piston you might need. If you don't premeasure it than that's your call but, if you intend to bore it you MUST bring the new piston with you. The new piston packaging box may also list the piston specifications needed for the shop to bore it correctly.

Originally posted by hornetgod13
Yes, you need to hone the cylinder whenever you change pistons. It's done to ensure the new piston rings break in properly.

I did not know that. When my brother got his piston and cam he just put it in.

[casey_lamm]

well i know a few that did that as well, but since its my bike I think I will have it done by the book...

btw... those that just dropped it in are fine...no problems.


Originally posted by FoxHondaRider
I did not know that. When my brother got his piston and cam he just put it in.

[hornetgod13]

Originally posted by casey_lamm
well i know a few that did that as well, but since its my bike I think I will have it done by the book...

btw... those that just dropped it in are fine...no problems.

I aggree with you about doing it right the first time. I bet your friends compression checks would have higher numbers if they had honed the cylinder prior to installing the new piston and rings

[X400EX]

I've installed a Wiseco 11:1 piston in my 2006 400Ex with all the mods in my sig.

It runs very well since may 2007, I ran it hard and got no problems.

I have not done anything to my stock cylinder. It was looking very nice and had no scratchs.

So, I'm still 397cc. :)

I was thinking of a JE 10.5:1 or something. Just bump up the compression a little bit. I havent tried JE but I have experience with Wiseco and I loved the fact that their pistons were so much lighterthan stock the bike revved quicker and the little added compression made it a good mod. JE I am willing to try because they have a 10.5:1 and Wiseco has 10:1. Probally wont notice much of a difference between the 2 idk. Are JE pistons lighter than stock too?

[hornetgod13]

11:1 isn't that radical of a step up. It should not ruin the reliability of the engine if it's done correctly. 12:1 or higher require a little more maintenance like heavy duty cylinder studs and racing gas.

I have heard nothing but good things about Wiseco and that's why I'm going with them. Not sure about the other brands.

[casey_lamm]

I have to agree with you.


Here is my shopping list..

C&D Racing
Hotcam stage 1
Weisco 11:1 stock bore piston kit
parking brake block
Top end gasket kit
Exhaust gasket
power airbox lid



Originally posted by hornetgod13
11:1 isn't that radical of a step up. It should not ruin the reliability of the engine if it's done correctly. 12:1 or higher require a little more maintenance like heavy duty cylinder studs and racing gas.

I have heard nothing but good things about Wiseco and that's why I'm going with them. Not sure about the other brands.

[hornetgod13]

I've got the motor all tore down and even pulled the old cam chain. I put the stock timing key back in too. I'm just waiting for parts to arrive. This is a list of things I'm installing.

1. 85.50mm (402cc) 11:1 Hi-Compression Wiseco Piston and Rings
2. Heavy Duty Cam Chain (CRF450 Cam Chain)
3. All New Seals and O-rings including new Valve Seals
4. EBC Dirt Racer Clutch Kit with HD Springs
5. Hotcams Stage 1 Camshaft

Total cost including boring cylinder=$456.00

[drew416ex]

Originally posted by FoxHondaRider
I was thinking of a JE 10.5:1 or something. Just bump up the compression a little bit. I havent tried JE but I have experience with Wiseco and I loved the fact that their pistons were so much lighterthan stock the bike revved quicker and the little added compression made it a good mod. JE I am willing to try because they have a 10.5:1 and Wiseco has 10:1. Probally wont notice much of a difference between the 2 idk. Are JE pistons lighter than stock too?

Yes the JE is roughly the same weight as the wiseco. And as a 10.5:1 compression is roughly the same compression too since the wiseco isnt a true 11:1 because of the deck height.

i'm yet to figure out why people say the wiseco arent the true compression. sure its very likely any piston could be off by a little but 11:1 being more like 10.5:1 doesnt seem logical

[drew416ex]

Its actually closer to about a 10.5 - 10.8:1 compression. Basically the piston doesnt go as close to the head as it could. I dont know about now, but when i had a wiseco in mine about 4 years ago, it had about 10.8:1 until i removed the base gasket and got the deck height a little closer. I never had a problem with the piston, but it wasnt a true 11:1. Maybe they have changed since then, i dunno.

i'm just looking for a little boost in compression and something to give my more performance. I know the lighter pistons make the bike rev quicker. What is stock compression? 9:1?

[casey_lamm]

10:1 I think.


Originally posted by FoxHondaRider
i'm just looking for a little boost in compression and something to give my more performance. I know the lighter pistons make the bike rev quicker. What is stock compression? 9:1?

Originally posted by casey_lamm
10:1 I think.

any verification to this?

[drew416ex]

Personally, i would go with 11:1 if i were you. It doesnt cost any more, you will have a little more power out of it, it wont be any less reliable, and you can still run pump gas.

[hornetgod13]

Originally posted by FoxHondaRider
any verification to this?

Yes, stock is 10:1.

then stock being 10:1 getting a 10.5:1 is almost stupid to pay that much for basically the same thing. 11:1 it is then. Thats about a 0.75HP increase over stock plus its lighter so the gains are a bit noticable. thanks

[casey_lamm]

i just ordered from cdracing he didn't have the piston in stock but said he will order it monday and ship it to me tuesday...

if you choose them you might want to order by monday for fastest delivery.


Originally posted by FoxHondaRider
then stock being 10:1 getting a 10.5:1 is almost stupid to pay that much for basically the same thing. 11:1 it is then. Thats about a 0.75HP increase over stock plus its lighter so the gains are a bit noticable. thanks

[drew416ex]

actually 9.1:1 is stock or at least thats what it was for a 2001

Originally posted by drew416ex
actually 9.1:1 is stock or at least thats what it was for a 2001

thats what i originally thought but according to everyone its 10:1. Does the Clymler or Honda manuals tell you the compression in them? They have a lot of info i wonder if thats in it

[drew416ex]

Its in my clymer and owners manual as 9.1:1

[X400EX]

It was 9.1:1 from my 2006, stock. Go to honda.com, in the specs it also says 9.1:1.

so then i will probally get the 10.5:1. 11:1 i'm not sure. I just want to do a piston for now and no cam.

[casey_lamm]

go 11:1 why not...its like this...you aren't going to bore...so why not get the most bang for the money. Go w/11:1 :)

or you could wait for 2 weeks and ill get some videos and review how I like it.


Originally posted by FoxHondaRider
so then i will probally get the 10.5:1. 11:1 i'm not sure. I just want to do a piston for now and no cam.

[REPOMAN]

i replaced my 440 with a stock motor when i blew the motor. i have the new motor tore down now and i am going 11.1 with a ported head. not sure if i want to go with a cam right now or even which one to get.

oh and i have my old cylinder and piston if anyone needs or wants a big bore. the bottom end is all that suffered when the motor went. heck the crank is still good to

is it only really high compression pistons tha make you blow gaskets?

[JOEX]

Originally posted by FoxHondaRider
is it only really high compression pistons tha make you blow gaskets?
Improperly torqued head bolts
Warped cylinder or head
Damaged cylinder or head surface

thanks JOEX. so my piston shouldnt interfere with my valves or anything else. just asking cause i have a 10:1 wiseco with a valve through it and melted in. it was probally the timing chain jumped a tooth or something. the piston had 2 rides on it :/

[JOEX]

Originally posted by FoxHondaRider
thanks JOEX. so my piston shouldnt interfere with my valves or anything else. just asking cause i have a 10:1 wiseco with a valve through it and melted in. it was probally the timing chain jumped a tooth or something. the piston had 2 rides on it :/
Shouldn't be any worries of piston and valve contact on the 400ex motor unless you start milling the head and/or cylinder.

[casey_lamm]

Joex or someone..

can you explain what porting does...and whats invovled to have it done?


Originally posted by JOEX
Shouldn't be any worries of piston and valve contact on the 400ex motor unless you start milling the head and/or cylinder.

there are different degrees of porting. If you look at all the stock heads they have casting flaws or marks and bumps that restrict the flow. A basic port and polish (cleanup) simply removes those casting flaws and the exhaust side it polished to a shine. Other port and polish jobs actually remove material and make the ports bigger and then they polish the exhaust to a shine. The exhaust ports being polished makes it so the carbon can not build up as easy.

[drew416ex]

Originally posted by casey_lamm
Joex or someone..

can you explain what porting does...and whats invovled to have it done?


Basically it improves air flow into and out of the engine. An engine is basically an air pump. The easier is is to get air into and out of, the more efficient it is.

[NacsMXer]

Originally posted by FoxHondaRider
i'm yet to figure out why people say the wiseco arent the true compression. sure its very likely any piston could be off by a little but 11:1 being more like 10.5:1 doesnt seem logical

I'm pretty sure it has something to do with the fact that the Wiseco pistons are designed for the XR400 dirtbike, which uses a thinner base gasket, acheiving more squish up top. Put the same piston in a 400EX and you get slightly less compression. I remember a lot of guys in the past eliminating the base gasket altogether and just using gasket-maker rtv to help get some compression back.