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EX-XX

Quick question around compression in a "long sat" engine.

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As some will know, I bought a spare engine, ostensibly from a 2000-model bike, with the idea of doing a 20-year refurb on it later this year (have coolant hoses, thermostat, O-rings etc. for it already).

 

Anyway, the engine supposedly had ~67,000kms on it, but has sat around for probably a couple of years.

 

Last Friday, I took the bare engine to a local, well-respected motorbike mechanic to have it compression tested. He asked how long it had sat for, and I told him probably around a couple of years. He mentioned that it was likely to have compression readings "all over the place", as it had sat for so long...And it did.

 

The readings ran from a low of 65PSI, through to ~115PSI. He told me that they would likely return to consistent readings once started and run for a bit. 

 

Question: What do you people reckon? Will they likely "normalise", or do I have a potentially dud engine?

 

 

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To be honest, it's impossible to say. Lubing up the cylinder walls before running and turning it over a bit

will certainly help. I wouldn't be surprised to see compression readings come up to close to normal. But,

and a big but it is, it's all about what it's like inside. Endoscopes are pretty cheap now, so you could pull

the plugs, and use the endoscope to check the condition of the cylinder walls.

 

I can't see getting reliable compression readings without the engine running in the first place. Things are

just going to be stuck, and not sealing. Did he do a leak-down test? Or how did he do a compression test

without the engine running?

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I would imagine the various rings would need to heat up and get oiled to get unstuck and a true compression reading. 

For my money I would update or upgrade the rubber hoses and o-rings on a constant used high mileage engine rather than roll the dice on an engine sitting collecting dust and corrosion. 

And I did. 103,000+ miles on my ‘99. All new silicone coolant hoses and new OEM o-rings sealing the water pipes to the engine. New t’stat o-ring. Sent my injectors off to be cleaned and flow matched. New fuel filter. Etc. 

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3 minutes ago, FJ12Ryder said:

To be honest, it's impossible to say. Lubing up the cylinder walls before running and turning it over a bit

will certainly help. I wouldn't be surprised to see compression readings come up to close to normal. But,

and a big but it is, it's all about what it's like inside. Endoscopes are pretty cheap now, so you could pull

the plugs, and use the endoscope to check the condition of the cylinder walls.

 

I can't see getting reliable compression readings without the engine running in the first place. Things are

just going to be stuck, and not sealing. Did he do a leak-down test? Or how did he do a compression test

without the engine running?

As a bare engine, he simply put a compression tester into each spark plug hole and turned the engine over on the starter. He did "have a look" in the cylinders, and noted they looked fine. He also noted some carbon build up (around valve seats and what not) which could be preventing effective sealing on the compression stroke...which goes to your point about things "being stuck and not sealing".

 

It's one of those things...

 

Do I take a punt on putting all the refurb "kit" on the "new" engine, or do I just replace all of the relevant bits and pieces on the existing engine with ~136,000kms on it (~85,000 miles).

 

On the other hand...I have had some thoughts about doing a "HighSideNZ-style" 825cc rebuild...

 

 

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20 minutes ago, EX-XX said:

 

On the other hand...I have had some thoughts about doing a "HighSideNZ-style" 825cc rebuild...

Yes, that’s what a dusty sitting engine is for!

And keep the high mileage (km, sorry) one going. It’ll keep running as long as you maintain and use it. 

Just my opinion, but based on my own ‘99. 

Another thought. It’s real rare, but I’ve heard of a gear box failing in a 5th gen maybe a couple times. Clutch basket a couple times. Broken chain taking out a sprocket cover and breaking the side of the case. Oil drain bolt stripping. In other words, just keep it around for spare hard parts.  

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My 2 cents.

 

I don't think the compression test is indicative of anything... except that the engine has sat around for a bit and not been run. There's alot of shiny surfaces inside that machine that only keep fresh by being used but will also refresh when used a little. Provided it hasn't sat too long or got wet or got dirt in it.

 

I would refurb it, stick it in your bike and then do a full rebuild on the high mile original engine, increasing its capacity etc once your exchanged engine has proved itself.

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On 2/12/2019 at 5:32 PM, EX-XX said:

As some will know, I bought a spare engine, ostensibly from a 2000-model bike, with the idea of doing a 20-year refurb on it later this year (have coolant hoses, thermostat, O-rings etc. for it already).

 

Anyway, the engine supposedly had ~67,000kms on it, but has sat around for probably a couple of years.

 

Last Friday, I took the bare engine to a local, well-respected motorbike mechanic to have it compression tested. He asked how long it had sat for, and I told him probably around a couple of years. He mentioned that it was likely to have compression readings "all over the place", as it had sat for so long...And it did.

 

The readings ran from a low of 65PSI, through to ~115PSI. He told me that they would likely return to consistent readings once started and run for a bit. 

 

Question: What do you people reckon? Will they likely "normalise", or do I have a potentially dud engine?

 

 

Your mechanic is right.  Once the engine is run for awhile you will notice that it gets better and better.An engine needs the pressure from the cylinder firing to help seal the rings. One thing that might concern me was the low of 65 lbs.  That seems pretty low to me even on an engine that has sat.

 

Once the engine runs the numbers will come up. If it was mine and I was going to keep it stored I would put a small quantity of oil down the cylinders and turn it over a few times to circulate the oil in the cylinders.  Change the oil & filter, then seal everything back up, intake & exhaust. There are some things you can do to help get rid of some of the carbon build up if you are going to install it or you could take the heads off and have the valves refreshed.

 

You really won't know what you've got until you install and run the engine.

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67,000km isn’t a lot. It certainly has lots of good life left. Hard to say what sort of life it led from the outside but if the bores look good down the plug holes then I’d just run it like cycleman1 and your mechanic suggest. 

 

If you have the time, money and itch to refresh valves etc then do it now. Otherwise just fit the lump and be happy. 

 

Not sure I’d do a big bore on your “older” engine though. Whilst these are bulletproof and can run forever, a big bore creates considerably more stress and the worn componentry might not be up for that. Wasted investment. 

 

If I was spending the coin on a big bore, I’d be looking for a low mileage donor whose gearbox, clutch, crank etc can better handle the abuse. Your “new” engine is a better candidate for big bore than your “old”, in my opinion. 

 

A lot will depend on what you intend to do with the bike. If you’re commuting, then just shim the valves and fit “new” engine. If you’re tracking it, then maybe look at spending on upgrades (valves, port polishing and/or big bore). 

 

Stray

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Did you do a wet compression test?

i would suspect the valves might have something to do with the low numbers. 

Any valve that was sitting in the open position is susceptible to a bit of corrosion forming and giving you low compression. 

If I had a spare motor sitting there, I would deffinetly pull the head and redo all the valves and springs/seals before I installed it. 

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I think we are all avoiding the very obvious here. Why remove a perfectly working “high” km engine in favor of another with “relatively” low km for no other reason than km used? It’s not brand new off the factory floor. Your current engine is showing no signs of performance degradation. Many, many engines of that vintage are running more kms without any issues.

Unless your OE engine is failing, keep it! 

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5 hours ago, BuzznerSuntrusts said:

I think we are all avoiding the very obvious here. Why remove a perfectly working “high” km engine in favor of another with “relatively” low km for no other reason than km used? It’s not brand new off the factory floor. Your current engine is showing no signs of performance degradation. Many, many engines of that vintage are running more kms without any issues.

Unless your OE engine is failing, keep it! 

 

Because we can.

I refuse to stop fideling with my bike, I know it makes no financial sense, but such is life.

I'm going to buy at 765 Street Triple R this year with plans to stick a Daytona fairing on it, once I do I will probably turn my 5G into a naked with major weight loss the target. Crazy I know.

Why? Because I can.

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Nah, take the spare engine apart, rebuild it with fresh parts and balance and "blueprint" it.  Then swap engines.  :happy:

 

Ciao,

 

JZH

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