TZR Compression

[Snorty]

After my TZR rebuild, perhaps 2/3 months ago, the compression was very high (the kickstart had a lot of resistance in it), and it had a lot of pull.

Now there is a noticeable difference in both these aspects, the kick start is quite easy to kick, and the acceleration isn't what it was. It still starts first time but I think the engine should have a longer life than this?

I don't ride this bike anymore but was hoping to let my girlfriend ride it. I can only guess that the bore is worn yet again, but could there be anything else causing low compression?

[hazza]

Loss of compression can be caused by many things. How many miles have you done since rebuild? has it been run in? Unusually smokey and using gearbox oil?
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3 Honda NC50's(Sold)-->'72 Puch Maxi S (Sold, want it back!)--> '90 Yamaha RXS 100 (Stolen)--> '87 Honda Cub 90(Sold) --> '95 Kawasaki Eliminator (Sold) --> '98 Bandit 600 (Sold) -->'07 SV650S (Current)

[Snorty]

Well before I passed my DAS I had it idling outside warming up as I was locking up at work, there was a pool of engine oil under the bike after I'd done, once it had leaked X amount it stopped.

The loss of compression had started before this, however.

Ran it in on fully synthetic oil from Esso, Mobil 2T. Not sure how many miles it's done, probs about 900/1000 miles since last rebuild. (Speedo doesn't work so I can't measure it).

Once thing I will say is it did fall over in the garden, the ground, like everything else on my landlord's property, gave way. The stand sunk down and it fell over. It was roughly around this time the bike started to perform worse. Couldn't say it was this for sure though.

[hazza]

where was the oil coming from?
if it were me, id whip the top end off to see whats going on. also Id take a look at the crank seals.
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3 Honda NC50's(Sold)-->'72 Puch Maxi S (Sold, want it back!)--> '90 Yamaha RXS 100 (Stolen)--> '87 Honda Cub 90(Sold) --> '95 Kawasaki Eliminator (Sold) --> '98 Bandit 600 (Sold) -->'07 SV650S (Current)

[Snorty]

It seemed to be coming from some sort of pipe? I don't know if there are any pipes attached to the gearbox, I have only ever messed around with the top end.

It wasn't after any recent changes though, I hadn't altered anything, just decided to piss oil that day. I'm guessing crank seals are a big job?

It only really smokes when I have the choke on and when the engine is still cold, about as much as I would expect from a 2T

[hazza]

If the seal has gone gearbox side, then you would expect a lot of smoke and diminishing oil levels! however if its gone flywheel side then compression would be reduced and the bike will be running lean as its sucking in air. Look at the spark plug, the colour and condition will indicate how its been running.
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3 Honda NC50's(Sold)-->'72 Puch Maxi S (Sold, want it back!)--> '90 Yamaha RXS 100 (Stolen)--> '87 Honda Cub 90(Sold) --> '95 Kawasaki Eliminator (Sold) --> '98 Bandit 600 (Sold) -->'07 SV650S (Current)

[Snorty]

Since I got this bike I've never been able to view the oil levels in the sight glass, like it's got a load of crap on the inside. When I had a full rebuild I could see it for a few weeks then it got all dark again.

Would changing the oil sort this out? To change the oil will I need a new drain plug or will I get away with re-fitting the same one?

[hazza]

Its not going to improve compression, but if its full of cack in there remove the side casing completely and clean the inside before refilling with oil or the problem will persist. Are you sure its not just condensation from not being used enough/ not getting hot enough?

You wouldnt need a new sump plug, but its always a good idea to get a new sump plug washer.

Best bet to diagnose the loss of compression would first to be see how its running by taking a look at the plug.
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3 Honda NC50's(Sold)-->'72 Puch Maxi S (Sold, want it back!)--> '90 Yamaha RXS 100 (Stolen)--> '87 Honda Cub 90(Sold) --> '95 Kawasaki Eliminator (Sold) --> '98 Bandit 600 (Sold) -->'07 SV650S (Current)

[Snorty]

Last time I checked it was brown, if anything on the lean side definitely not too rich.

Will check how it looks next time we get a nice day.

On a side note, one of the previous owners painted the entire frame/subframe with white paint... some of it is chipping off I'm guessing it wasn't special paint. I'm thinking of removing it, what would be the best way?

Would something like Nitromors work?

[hazza]

Is it the later tzr 125 i.e not the late 80's/early 90's tz125r? If you want to repaint the frame its going to be a complete strip down job. It all depends on how much you want to spend....Powdercoating is going to give the best finish and the process dosent take very long, but will probably cost a couple of hundred quid. They will shot blast it first to ensure a perfect finish. Nitromors would certainly remove the paint to a bare metal finish but you would have to be careful with it. If repainting i would be tempted just to sand it if its flaking off easily already, then spray hammerite it for about £11 a can.

On the compression side, as you said brown is good, but leaky crank seals would make it run lean, not rich.
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3 Honda NC50's(Sold)-->'72 Puch Maxi S (Sold, want it back!)--> '90 Yamaha RXS 100 (Stolen)--> '87 Honda Cub 90(Sold) --> '95 Kawasaki Eliminator (Sold) --> '98 Bandit 600 (Sold) -->'07 SV650S (Current)

[Robby]

There is the chance that when it fell over it was 2 stroke that was leaking out, rather than gearbox oil. Check that you still have 2 stroke oil in the tank, and look to see if any of the 2 stroke oil lines have been disconnected or split.

[Snorty]

It's the 2RK, early model.

I was just thinking of stripping it down to the bare metal as it looks nicer than the crappy white paint.

The sandpaper isn't a bad idea actually, genuinely hadn't thought of that lol.

Bike's not really worth powdercoating, just would be nice to make it look like a decent specimen of a TZR, who knows when I might need to use it again!

I think all the 2 stroke pipes are intact, it hasn't seized up in the month or so I used it since it fell over. (12 miles a day).

[hazza]

Are they the deltabox steel frames? if so its going to need some sort of protection from rust! if its alloy you could really take your time and polish it.

Check out my thread on alloy polishing here:

https://www.bikechatforums.com/viewtopic.php?p=2880138
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3 Honda NC50's(Sold)-->'72 Puch Maxi S (Sold, want it back!)--> '90 Yamaha RXS 100 (Stolen)--> '87 Honda Cub 90(Sold) --> '95 Kawasaki Eliminator (Sold) --> '98 Bandit 600 (Sold) -->'07 SV650S (Current)