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Buell Motorcycle Forum » XBoard » Buell XBoard Archives » Archive through March 03, 2008 » 05 XB12R engine cam-drive type « Previous Next »

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Ochoa0042
Posted on Monday, February 25, 2008 - 05:11 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

what type of cam-drive system does the XB12R have? push-rod or chain?

I was on a 6 mile straight almost maxing out, but I didn't fully GO~GO.
From the outer looks of the engine, it looks like a push-rod, but then again I don't know what a push-rod looks like. And push-rods are know for failure at high-extended rpm's use
I'm pretty sure its not push-rod, b/c Eric Buell would know better, but it is just a caution

please tell me that it is chain-pulley & camshaft!!
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Damnut
Posted on Monday, February 25, 2008 - 05:16 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

can't tell you that
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Elf
Posted on Monday, February 25, 2008 - 05:26 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

The valves are actually actuated by sheer force of will by the rider, driven through the Powerband!






Actually, the XB engine is pushrod.

A lot of people seem to think of pushrod engines as "old" or "low-tech".

They may not rev to the moon like an OHC, but don't discount the pushrod engine.

Here's an example of a pushrod engine:

http://jalopnik.com/337672/detroit-auto-show-explo ding-the-2009-corvette-zr1s-brilliantly-beautiful- ls9-engine

On the bright side, no valve adjustments needed on the XB! And no timing chain issues either!

(Message edited by elf on February 25, 2008)
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Drfudd
Posted on Monday, February 25, 2008 - 06:54 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

yeah, don't discount a pushrod engine. The viper engine is still pushrod
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Jos51700
Posted on Monday, February 25, 2008 - 07:06 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Ummmmm, technically, to answer this question, one must say "Gear".

The XB uses 4 gear driven cams, and uses pushrod *valve* actuation. with a set of 4 roller lifters, one per cam shaft.

Pushrods don't have anything to do with cam-drive, per se.
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Jos51700
Posted on Monday, February 25, 2008 - 07:17 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Being a pushrod motor doesn't really have much effect on engine longevity at high-RPM (assuming you're not over-revving it. The bottom-end parts are the same regardless of cam/valve operation). A pushrod engine typically doesn't make lots of power at high RPM, because the added mass of pushrods, lifters, rocker arms, etc, prevent rapid opening of valves (valve float).

The method of cam drive has little effect on RPM capability. For example, the 1125R uses chain AND gear drive for it's cam shafts (No pushrods). Chain drives one cam, and that cam gear-drives another cam.

On the Righthand side of your XB, there are two gray-black plastic covers, one on each cylinder, with a pegasus logo on them. These are your pushrod tube covers. A pushrod is simply a steel rod or tube (tube on XB, because oil travels up the tube to lubricate the valves and rocker arms), with round ends and a small hole in each end for the oil passage. Older pushrods for cars sometimes had a cup end, and the ball was on the rocker arm.

While I'm thinking about it, the Viper has a chain-drive cam.

Howstuffworks.com has some great sites about it all.

http://www.howstuffworks.com/engine.htm

(Message edited by jos51700 on February 25, 2008)
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Jos51700
Posted on Monday, February 25, 2008 - 07:23 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Even betta!

http://auto.howstuffworks.com/camshaft1.htm
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M1combat
Posted on Monday, February 25, 2008 - 08:37 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

It's a pushrod engine.

The stock pushrod setup for the XB's is good to about 8300-8500 RPM without float. You're good there : ). You can raise that quite a bit with aftermarket parts. That said... The stock valve train won't last a long time at 8500 : ) and the front conrod and the crank shaft won't last very long at all at those RPM's.

One of the cams is actually ON the crankshaft. That one drives the two nearest it and the fourth is driven off of one of those.

Apparently the weaknesses of the engine are the front connecting rod, the stock oil pump drive gear (before '06), the left side main bearing and the rear exhaust valve (like all harleys).


So did you break something?


I'm just wondering cause I've had mine over 110MPH for probably 5K miles and over 130 for probably 300 (on a closed course of course...). I left the throttle absolutely pinned once for about an hour. From one gas station to the next (The gas stations were on a racetrack...).


It finally destroyed the old style oil pump drive gear at 51K miles. I MAY have also stretched the front conrod so I replaced the crank/rods with the '08 crank and slapped a set of custom forged CP pistons in it along with a mild street port and a compression bump. I couldn't find replacement stock pistons (+.010" or +.015") so I had the pistons custom made. I'll have it back together this weekend as long as I've planned well : ).


So anyway... Did it break or something?



And -

"Erik Buell would know better."


Hmmm...

Notable modern pushrods...








You'll notice those two yellow ones are in front of a no pushrod having Porsche. An older version of the red one won Le-Mans 3 or four times... In a row. Oh yeah... same with the yellow ones : ).

My only point is that there are many ways to skin a cat. One of them is RPM (Chain driven OHC and that sort of thing), another is displacement, another is less mass, another is aerodynamics...



/EDIT = ON

Being a Ford guy I REALLY wish I had another pic of some modern blue Le-Mans winners for you.

(Message edited by m1combat on February 25, 2008)
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Jos51700
Posted on Tuesday, February 26, 2008 - 07:41 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

"One of the cams is actually ON the crankshaft."

Wrong. 4 cams. One driven FROM the crank, (front cyl. intake), that drives two (Rear intake and front exhaust), and then rear intake drives the rear exhaust.
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Xl1200r
Posted on Tuesday, February 26, 2008 - 08:33 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

^^ +1

4-stroke engine means the cams need to turn half as fast as the crank.

Our cams are all gear driven.

I don't think it's been said but having a chain driven cam doesn't mean the engine has to be OHC. Just about every single OHV car engine out there that I can think of has a chain driven cam, it just sits low in the block rather than on top of the head.
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M1combat
Posted on Tuesday, February 26, 2008 - 03:45 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

"Wrong. 4 cams. One driven FROM the crank"

Sorry 'bout that : ). Don't know what I was thinking.
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Jos51700
Posted on Tuesday, February 26, 2008 - 04:02 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

"Sorry 'bout that : ). Don't know what I was thinking."

I'm guessing that what you meant to say was "one runs on the crankshaft," (or something similar) and left a word or two out. I do it all the damn time. Fingers are forgetful, or something. No matter. I will ALWAYS respect someone that can admit fault.
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Jos51700
Posted on Tuesday, February 26, 2008 - 04:04 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

How do you guys post el biggo pix? My pics are always small, and none too manly. When I try to post manly pics, it says they are too manly, and must be castrated.

That's very frustrating when I'm trying to tie up bandwidth.
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M1combat
Posted on Tuesday, February 26, 2008 - 07:32 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Oh no : ), I meant to say one was on the crankshaft... I still don't know what I was thinking though : ).

Use xat for image resizing : ).


http://www.xat.com/jpegopt/index.html
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Jos51700
Posted on Tuesday, February 26, 2008 - 07:43 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

I've used photoshop to shrink photos, but if I post by BadWeb guidelines, it's postage-stamp no matter what. I also get a prompt on EACH page, wanting to know what username I want to use, even though they're all the same.....
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M1combat
Posted on Wednesday, February 27, 2008 - 01:59 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Use xat for image resizing : ).


http://www.xat.com/jpegopt/index.html
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Ochoa0042
Posted on Wednesday, February 27, 2008 - 03:12 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Well it sux to find this out, but better tho know.
Pushrods are meant for low-rev torquie engines. At high-temps, high-rpm, & High-heat, they are prone to fail disasterously!

M1,
where can you find a road that you can go 110mph for an hour? woah Since your engine failed, mainly pertaining to the rods(i think), it doesnt put too much confidence.

But like I said, push-rod engines are meant for low-rev torquie engines. The corvette and viper are large displacement(torquie) low-rev type cars, so they meet up to the standards of what push-rod has to offer, and so does the XB12

So im not to worried about failure anymore, unless I go out for a 2hour engine-pinned max-speed thrill ride, thanks for the help y'all!
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Bombardier
Posted on Sunday, March 02, 2008 - 12:49 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

May I suggest you have a look at the Buell website and listen to what Erik Buell says about cornering and straight line high speed riding.
I happen to subscribe to what he says as he is a successful racer in his own right.
You may get beaten on the straights by the high revving metric bikes but most will not catch you on the bends.
Different strokes for different folks.
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Old_man
Posted on Sunday, March 02, 2008 - 03:59 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Corvettes have push-rod engines among many other American high performance engines.

The hydraulic lifter push-rod engine is one of the reasons I chose to buy my Buell.
Never have to adjust the valves.
A very reliable set-up.
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Blake
Posted on Sunday, March 02, 2008 - 07:51 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

James (Ochoa0042),

You've been misinformed, at least wrt Buell engines. The record of pushrods as far as reliability and durability far surpasses some other forms of camshaft actuation. I can't tell you how many times I've heard of cam belts failing. Chains, not so much.

When it comes to Buell engine failures, you hear about holed pistons, oil pump drive gears, poor ring seal, and the like.

You don't often hear of pushrod failures; I'd have to say that from my view they are one of the rarest of serious mechanical engine failures you ever hear about. It's certainly not a major issue of concern for Buell's engines.
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Birdy
Posted on Sunday, March 02, 2008 - 07:58 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Heck I love push rod motors. After I broke a timing belt of a Honda b15 motor (car VTEC) and it was a $5000.00 pile of poo I gave up on that whole way. Of course at the time I was turning it at about 9500 rpm!

You don't HAVE to rev a Buell to the limit to get power I rarely get over 5000 rpm and my only worry is John Law!
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