Author Topic: Can I just rebore one cylinder? ( 400/4) (Read 8824 times)

neilma · « **on:** November 21, 2009, 01:57:06 PM »

Is it acceptable to just go oversize on one cylinder and leave the others stock? One of the rings broke in the #1 cylinder leaving some deep scores so I will get that rebored to 0.25 oversize. However, the other bores are all fine so I thought I would just get them honed and use the standard pistons with some new rings? Is that ok or should you go oversize on all of them?

Sorry for the questions

I am sure there will be many more to come until I have this thing built back up

mystic_1 · « **Reply #1 on:** November 21, 2009, 01:58:47 PM »

Your pistons would be different weights, that's not a good thing.

mystic_1

MacM2010 · « **Reply #2 on:** November 21, 2009, 02:16:15 PM »

I considered the same thing on my 750, but mystic is right.

I ended up getting a new sleeve and piston at stock size instead of a new set. LA Sleeve (www.lasleeve.com) is a good source, and will probably be cheaper than an overbore and 4 new pistons.

kghost · « **Reply #3 on:** November 21, 2009, 05:48:04 PM »

You can remove weight from the oversize piston to match.....

Terry in Australia · « **Reply #4 on:** November 21, 2009, 05:57:26 PM »

My older brother had a BMW R69S back in the 1970's that supposedly had a 50cc larger piston on one side, but it made no difference, even though theoretically, it should have vibrated itself to death with uneven reciprocating weights, combustion velocities etc. But like Tim has suggested, it may be that the shop took some weight off the larger piston to even things out. I'd personally just install a big bore kit and bore out all the cylinders. Cheers, Terry.

the technological J · « **Reply #5 on:** November 21, 2009, 09:10:47 PM »

im gonna play the devils advocate and ask why not over bore the two that balance each other ( like 1 and 4 or 2 and 3) then (in theory) shouldnt they balance each other out?

mystic_1 · « **Reply #6 on:** November 21, 2009, 09:21:22 PM »

1+4 don't balance each other out, they move together. In fact, the combined weights of 1+4 cancel out the combined weights of 2+3.

I can just see it, years later someone is gonna join the board and post in the "Worst thing your PO did" and tell us all about his bike where one piston is larger than the rest!

mystic_1

the technological J · « **Reply #7 on:** November 21, 2009, 09:25:21 PM »

i guess on second thought why not just over bore them all now take the finacial hit and enjoy the extra dispacement

754 · « **Reply #8 on:** November 21, 2009, 10:03:53 PM »

You guys worry way too much..

Its a wonder you got bikes after paying for your Testicle Matching surgery, and the Breast Matching surgery for the women in your lives...

..just run a .25 over in it...

heaven forbid one of your compression readings gets lower. than the other 3.....

MacM2010 · « **Reply #9 on:** November 22, 2009, 10:02:16 AM »

Does the stock piston look like it'd still work? That might be a factor - if it's reusable, you need a sleeve and rings. Then you have a perfect stock setup.

I guess it doesn't matter that much, it'll still vibrate less than a lot of bikes, but I'd hate to have the thing open and then put in a setup I knew was wrong. I'd be giving that cylinder the ol' stink-eye every time I got on the bike.

And my testicle-matching surgery was a graduation present, thank you very much.

the technological J · « **Reply #10 on:** November 22, 2009, 08:52:35 PM »

Quote from: 754 on November 21, 2009, 10:03:53 PM

You guys worry way too much..

Its a wonder you got bikes after paying for your Testicle Matching surgery, and the Breast Matching surgery for the women in your lives...

..just run a .25 over in it...

heaven forbid one of your compression readings gets lower. than the other 3.....

thats not fair..... i should have never told u.... they're mine now..and leave her outta this

Trevor from Warragul · « **Reply #11 on:** November 22, 2009, 11:19:49 PM »

It's quite common for Kawasaki 2 stroke triples to run different size pistons. I don't think you'd notice the difference on a 400/4 (the weight difference would be very small).

Go for it!

Trevor

Big Jay · « **Reply #12 on:** November 22, 2009, 11:46:34 PM »

On a 400, There would hardly be any weight difference. Go for it.

Jay

patrickd · « **Reply #13 on:** November 23, 2009, 01:51:38 AM »

Dude, that is a stupid idea. Yea, you can remove weight, but that aint gonna do #$%*. you're still gonna have one cylinder putting more power to that side of the crank than the other is putting on the other side. You already got the jug off, you still gotta replace the same # of gaskets If you want it to run well for a long time do it right. Nothing worse than a cheap mechanic

HawaiiMike · « **Reply #14 on:** November 23, 2009, 06:07:21 PM »

Just get a 466cc big bore kit and enjoy! Yeah it will cost some money. It will also transform your 400F into a mean street machine.

I had one 29 years ago and loved it. So did someone else, they stole it.

754 · « **Reply #15 on:** November 23, 2009, 07:54:04 PM »

Patrickd,
check your compression, you too may have a cylinder or two putting more power to one side of your crank.. then what are you gonna do?

steamnjn23 · « **Reply #16 on:** November 24, 2009, 01:57:20 PM »

all this therory talk is making my head hurt.

just do it, so we'll all have a real world experience to learn from

ColinMc · « **Reply #17 on:** November 24, 2009, 02:11:33 PM »

I did this in an 88 Yamaha FZR1000 I used to own...bike ran great and never had a problem with vibration or any of that crap. I was on a budget, got the bike for 200 bucks didn't want to put a ton of money into it...rode it for 2 years then sold it to someone else for 500 and told them all about it...still see it riding around the area no idea if he ever did anything else to the motor.

mlinder · « **Reply #18 on:** November 24, 2009, 02:14:15 PM »

Not a good idea. Upsets balance. There's a reason we balance carbs and engine parts to as close a tolerance as we can manage within financial constraints.

BobbyR · « **Reply #19 on:** November 24, 2009, 02:26:53 PM »

Back in the day Richard Petty realized they only checked the #1 cylinder for displacement using an air device before a race since it was easy to get to. #1 was stock and the other 7 were bored out to the max. He did OK. Like Terry said this is not a spacecraft.

mlinder · « **Reply #20 on:** November 24, 2009, 04:36:00 PM »

Not sure when he started doing that, but my bet is the engine was rebuilt fairly frequently. Like, probably close to after every race.
It's also 1/8th of the engine off balance instead of 1/4th.
The 400 is also an engine that likes to run at 10 grand.
The 400 is also almost 40 years old.

Hate to be disagreeable, but no, I wager it isn't the best of ideas.

BobbyR · « **Reply #21 on:** November 24, 2009, 04:52:27 PM »

Quote from: mlinder on November 24, 2009, 04:36:00 PM

Not sure when he started doing that, but my bet is the engine was rebuilt fairly frequently. Like, probably close to after every race.
It's also 1/8th of the engine off balance instead of 1/4th.
It's also an engine that likes to run at 10 grand.
It's also almost 40 years old.

Hate to be disagreeable, but no, I wager it isn't the best of ideas.

The King started doing that until some disgruntled guy turned him in. He then started hiding a small NOS bottle in the fuel tank which gave him those amazing finishes. Smokey Yanuck wrote about the tricks they pulled on NASCAR back in the day. He found in the rulebook that there was no fuel line diameter limit, so he started using I think 2" or larger pipe. Held an extra gallon of gas. Very interesting read.

mlinder · « **Reply #22 on:** November 24, 2009, 04:54:44 PM »

Quote from: BobbyR on November 24, 2009, 04:52:27 PM

Quote from: mlinder on November 24, 2009, 04:36:00 PM
Not sure when he started doing that, but my bet is the engine was rebuilt fairly frequently. Like, probably close to after every race.
It's also 1/8th of the engine off balance instead of 1/4th.
It's also an engine that likes to run at 10 grand.
It's also almost 40 years old.

Hate to be disagreeable, but no, I wager it isn't the best of ideas.
The King started doing that until some disgruntled guy turned him in. He then started hiding a small NOS bottle in the fuel tank which gave him those amazing finishes. Smokey Yanuck wrote about the tricks they pulled on NASCAR back in the day. He found in the rulebook that there was no fuel line diameter limit, so he started using I think 2" or larger pipe. Held an extra gallon of gas. Very interesting read.

Not a fan of modern nascar, but that sounds like awesome reading of some good ol' car racin'. Book name?

mystic_1 · « **Reply #23 on:** November 24, 2009, 05:29:40 PM »

Quote from: mlinder on November 24, 2009, 04:54:44 PM

Not a fan of modern nascar, but that sounds like awesome reading of some good ol' car racin'. Book name?

+1

mystic_1

BobbyR · « **Reply #24 on:** November 24, 2009, 06:38:47 PM »

Here is is website. My friend drives Indy cars and he lent me the one on speed secrets. This guy was a trip and a half.http://www.smokeyyunick.com/

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Author Topic: Can I just rebore one cylinder? ( 400/4) (Read 8824 times)

patrickd