Track Bike - Plan B

[RuZty]

Before you sit down to write chapter 6;

Option A - Buy/build a kit to pressure test the engine cases. (a tool that I would only use once or twice).

'Most' people only use an engine stand once or twice.

PS. When working on the motor, and in particular, when bolting the engine cases back together,
the engine stand is worth it's weight in gold.

....Should read 'When riding my bike for the 3rd summer in a row, and in particular, without having to rebuild it, the pressure tester I only used once is worth its weight in gold.'

I am not inclined to disagree with the likes of Slinger, Kenny or Brian Turfrey either, have you checked everything they suggested if any of those components are still in the engine?

Even if it wasn't an air leak last time you will never know if you have one now unless you check it, and when it goes bang you won't be able to test it again and rule that out as a cause.

Stop torturing yourself.

[Off Road]

On April 26, I posted a pic of the bike.



Haven't even looked at the bike for the last 3 weeks because I've been busy / lazy / unmotivated.
Tonight I was looking at the bike, and casually took off 1 part, then 1 more, then another, and before I knew it I was reaching for tools.
Didn't get very much accomplished, but every little bit helps.




But, I'm getting ahead of my self. Let's back up for a moment.
I'd like to thank RuZty, for his post.
Very perceptive. You are correct. I did Not pressure test my engine.
And you're post was great. A very polite, well written, humorous way of telling me to, "stop being a dumb-ass".
Well done.

As RuZty pointed out, a number of well respected, experienced, knowledgeable, engine builders, told me to pressure test the motor..
And despite all their good advice, I decided not to do it.

After hearing this confession, you're probably thinking 3 things.
1 - He's an idiot
2 - Why? Why would he not pressure test?
3 - He's an idiot.

Well, here's my feeble explanation.

1 - I didn't have $300 to buy a Motion Pro pressure test kit.
2 - I didn't have time, or the desire to run all over town sourcing parts, and then assembling a pressure tester.
3 - I don't think I have an air leak.

Before the bike seized last Summer, it ran perfect.
OK, probably not perfect, but it ran pretty good.
- Started on 3 or 4 kicks,
- Had a smooth steady idle, (hot or cold)
- Pulled away from a stop without any hesitation,
- Had a bit of a 5K stumble, but pulled hard from 6K to 9500 rpm.

And then, all of a sudden, for some unknown reason, after running great for 600 miles, the Right cylinder overheated, detonated, overheated, and seized.

A few years ago, I had a base gasket leak one of my other bikes, and it was immediately obvious.
I've been taking to a couple of fairly knowledgeable guys, and I've read a bunk of posts, and I'm cheap, and I'm lazy,
and I've manged to convince myself that my engine cases didn't leak.

So, I slapped the motor back in the bike, fired it up, and put 130 miles on it.
It runs perfect.
OK, probably not perfect, but it runs pretty good.
- Starts on the 2nd,
- Has a smooth steady idle, (hot or cold)
- Pulls away from a stop without any hesitation,
- Has a bit of a 5K stumble, but pulls hard from 6K to 8000 rpm.

Hmmm. That sounds familiar.

The only problem/concern that I see, is that the Right spark plug looks "different" than the Left plug. WTF's up with that?
(Could just be I'm just being paranoid, but I don't like it)

When I "rebuilt" this motor last Winter, all I really did was bore a couple of cylinders, and install a bigger set of pistons, along with some new oem gaskets.
After 130 miles of riding, I assume the rings have seated, and the engine's broke in.
So, 3 weeks ago, I pulled the tank off, and checked the compression.

122 psi - Left Cylinder
124 psi - Right Cylinder.




Hmmm. A little bit down from what I was expecting.
I was getting 130 psi, using this o-ring head with my old 31K cylinders.
Maybe it'll still come up some.

And that brings me to tonight.
Engine has reasonable compression.
It starts good, it idles good, it accelerates good, it pulls hard from 5500 to 8000.
It runs fine, I don't see any indication that it has an air leak.

So here I sit, Convinced that I don't have an air leak.
Paranoid that I do still have an engine problem.
And Glad that I know the right people, and have enough spare parts, so that I can rebuild the motor again for only $140 and a case of beer.


However, if it doesn't have an air leak, then why does it keep seizing the Right cylinder.
And did any of the small changes that I just made to the bike last Winter, fix whatever problem I had.
And if I didn't fix the problem, when is it going to seize again. 600, 700, 800 miles?
And what's changing, so that all of sudden, without warning, this engine goes from running good, to catastrophic failure?
And how do I know if it's going to happen again?
And why do the plugs look so different?
And Ya, I'm wee bit paranoid.

Fortunately, I have a plan.
It may not be the smartest plan that I've come up with, but it definitely won't be my worst plan.
At the very least, it should be fun and entertaining.

Box of new parts arrived yesterday
Won't be able to work on the bike until tomorrow. I'll wait until then to open it up.
But I am kinda excited to see what it looks like

[hondaror]

Steve, that's the same box you showed me yesterday at work. C'mon, open it. You love baiting!

[two-stroke-brit]

would a EGT set up give warning of an air leak/immanent meltdown?
mark

[evan_calgary]

EGT would likely tell you if your running hot but doesn't help identify the problem and its just a waste to keep melting down your motor....Seriously, its like $20 in parts to put together a pressure tester. I had air leaks in places I didn't expect in the least, with gaskets and gasket goo. Its really really backwards to do it this way. Basically anything you do will lead you in a big circle ending with smashing your head on the wall and you can't single out any issues.

[JonW]

There is a chap on Norbos forum selling leak down test kits, his name is Dan, username is maccas (or close to that), great guy too.

http://rdlccrazy.proboards.com/thread/3 ... -leak-test" onclick="window.open(this.href);return false;

[RuZty]

...horse..
...water..

[hondaror]

You can't...

[vonzipper]

Ok Steve the horse is starving, feed it some GRASS, open the box for heavens sake, lets see what ya got.

[Off Road]

I've had a number of knowledgeable, experienced people tell to pressure test my cases.
I want to thank everyone for their comments. I appreciate you taking the time to try and help.

I've also had an equal number of knowledgeable, experience people say that, based on the way my engine ran, it doesn't have an air leak.

So, in my infinite wisdom, or complete ignorance, or utter stupidity, (Your call),
I have embarked on a course of action and relocated the new parts from the box, to the bike.






The Kosso EGT gauge has 2 wires running from it. Each wire has a 2 pin connector on it.
The wires are just long enough to run from the top tree, to the inside of the of the frame, right in front of the PV servo.
(Which is great, because that's about the only place that they would fit)

The straight-line distance between the connectors and the EGT probes mounted in the pipe, is 12". ONE foot.
The braided steel lines attached to the probes, are SIX feet long.

OK, Need to hide 5' of braided steel cable and make it look neat, without kinking or bending the cable.

The Left Probe cable runs under the engine,
crosses over to the other side of the bike,
runs up the Right down-tube to the top of the rad,
curves back and follows the frame rails to the back of the carbs,
loops around the Right carb (where it meets with the Right probe cable).
Both probe cables then run up between the carbs, and over the middle of the head, where they plug in.
Piece of cake.







The instrument panel is no longer Stock.







The Left cylinder Always runs great.
Right cylinder runs good for quite a while, and then spontaneously combusts. Why?
What's going on in the motor, that causes this to happen?

OK, if 1 piston's running good, while the other piston's melting,
then I'm assuming that there's going to be a noticeable difference it the EGT's, of the 2 cylinders

Since I've had no problems with the Left cylinder, I'll "assume" that the EGT on the Left cylinder is ideal, and use it as a reference.
Then see how the Right EGT compares to the Left, as the load and throttle positions change.

I'll ride another 50 or 100 miles on the road, to see what info I can get from the gauge.
If nothing blows up then I'll do some fine tuning / torture testing on the dyno.


All that's left to do now, is wipe the dust off the tank, fire it up, and take this little engine experiment out on the road.
Only fear and good judgement holding me back.

[hondaror]

Steve, this just occurred to me, but carbs. Has your carb set-up remained constant? Do you know for sure that the main jets are unmolested? People often drill them out and neglect to mark new hole size. Just a simple thought.

[Off Road]

The carbs have been changed in the past.
Last year when it seized I was running the Toomey 420 main jets.
This year I installed a new set of Mikuni 420 main jets, and new Mikuni pilot jets.

[hondaror]

That's good that you know what is in there for sure.

[Off Road]

Speaking of engine experiments.

Last year, I was running 31K cylinders and one of Slingers O-Ring heads.
Compression was measured at 130 PSI.

This year, I'm using the same head, but I running a set of 1UA cylinders.
Compression was measured at 124 PSI.
I was.........miffed.


A few weeks ago, I read this on the forum.

Early models, 83/84 have a Y-1 head. 85-90 have a Y-2 head. The Y-1 head has a slightly larger volume and, thus, should not be used with 1UA cylinders as the 1UA raised ports require a head with a smaller volume to maintain the proper compression ratio.

I hadn't seen this information before, but it got me to thinking.
"IF" I understand the 2 stroke motor, and I'm really not sure that I do, but I think that the engine starts compressing the air/fuel mixture, After the exhaust port closes.

The 1UA exhaust port is 1 mm higher than the 31K port, so the piston travels 1 mm Less, from the time the exhaust port closes, until it reaches TDC.
Since the piston is moving a shorter distance, it will decrease the amount of compression of the air/fuel.
Lower compression will result in Less HP.

So, I could be completely wrong about all of this. If I am, then someone please help out by posting some correct information.

However, if I'm correct, and 1UA cylinders do lower the compression and reduce HP, then.............I'm really miffed.


On the bright side of things, there's still a pretty good chance that I'll seize this motor again, in which case, the amount of HP it made will be irrelevant.

[silverstrom]

However, if I'm correct, and 1UA cylinders do lower the compression and reduce HP, then.............I'm really miffed.

And yet the 1UA makes 4 HP more than the 31K. You worry too much. Spend that time and energy pressure testing your cases.