Where to start - putting it back on the road

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two-stroke-brit
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Re: Where to start - putting it back on the road

#151 Post by two-stroke-brit » Thu Sep 10, 2015 2:00 pm

i never liked the Marlboro paint scheme but i am warming to it.
She might not be pretty but always a fun ride !!

PaulGreen
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Re: Where to start - putting it back on the road

#152 Post by PaulGreen » Thu Dec 13, 2018 11:57 am

Well after a 6 year hiatus (YIKES!) I've had another look at this project....

I set the carbs up properly on the bench, threw them on the bike and turned the engine over a few times. Then i turned on the ignition and kicked it and.... nothing.
1 new ignition coil later and I tried again the next day. It spluttered on the 2nd kick and.... I suffered a hydraulic lock!
After taking the top end off I found that the upper cylinders were full (literally) of 2 stroke, so Ive ordered new check valves for the oil pump.

Today I got it all bolted together again and..... she lives (ish). It's running on 2.5 cylinders - the fronts are fine. I suspect its ignition as I can smell petrol from the exhaust.
It sounds kind of big endy, I'm really hoping that's just because it's only firing on 2.

Anyway, progress, of sorts.

Cheers,
Paul.

lost1750GTV
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Re: Where to start - putting it back on the road

#153 Post by lost1750GTV » Thu Dec 13, 2018 4:46 pm

yes, I'm very late to the party.
from "recent" experience I can tell you it sounds much nicer as a triple than as a twin, and I'd say your "big endy" description is as good as any. nice thing is you can check each exhaust tip for smoke/compression/nothing?

my son suggested I bring it into the basement to work on it over winter and I told him something like your prior page post, Aug 29 2012 8;58pm haha. maybe for wheels and stuff but not for carbs.

he remembers when he was a kid I had the TZ (and others) in the basement. I guess he forgot about the divorce that followed very shortly.
well, I'm not doing that again haha

PaulGreen
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Re: Where to start - putting it back on the road

#154 Post by PaulGreen » Sat Dec 15, 2018 1:51 pm

Today I've swapped the ignition coils over and it still only started on the front 2 although the rears came on for a bit.

Looking at carbs next, see what they look like again.

silverstrom
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Re: Where to start - putting it back on the road

#155 Post by silverstrom » Sat Dec 15, 2018 4:48 pm

I can't see it being carbs. It seems unlikely that both rear carbs would be problematic while both front carbs are fine. Not impossible, but I would continue with eliminating electrical issues for now. I have commented in your other post regarding this. Carb issues are often confused with electrical issues, and vise-versa, due to similar symptoms.

PaulGreen
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Re: Where to start - putting it back on the road

#156 Post by PaulGreen » Sat Dec 15, 2018 5:53 pm

I thought carbs unlikely, too, due to the nature of the issue. The front/rear split points elsewhere.
However, tonight I've noted crud in two of the freshly cleaned float bowls - I haven't checked the other side yet - and the in-tank filter is filthy. I can smell petrol from the cold exhausts so I don't think that's causing the problem but it obviously needs sorting.
So before I go any further I'm cleaning the fuel tank of rust using the electrolysis method I've used before. I'll see where we go from there.
In the mean time I'll follow up on your other suggestions .

Thanks again,
Paul.

silverstrom
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Re: Where to start - putting it back on the road

#157 Post by silverstrom » Sat Dec 15, 2018 7:23 pm

Hopefully it's that simple. You can try running the engine on a portable fuel bottle once you get the carbs cleaned.

These things can be so frustrating. You get to what you think is the easy part of the restoration and it all goes sideways for no apparent reason. Keep at it. You're almost there.

rd84
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Re: Where to start - putting it back on the road

#158 Post by rd84 » Sun Dec 16, 2018 1:04 pm

PaulGreen wrote: Sat Dec 15, 2018 5:53 pm I thought carbs unlikely, too, due to the nature of the issue. The front/rear split points elsewhere.
However, tonight I've noted crud in two of the freshly cleaned float bowls - I haven't checked the other side yet - and the in-tank filter is filthy. I can smell petrol from the cold exhausts so I don't think that's causing the problem but it obviously needs sorting.
So before I go any further I'm cleaning the fuel tank of rust using the electrolysis method I've used before. I'll see where we go from there.
In the mean time I'll follow up on your other suggestions .

Thanks again,
Paul.
Good luck Paul - Its quite a big job so stay patient - check inside the fuel tap - definitely go with Viton replacements for seals, diaphragms and float valves while its in bits.

Cheers
Paul

PaulGreen
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Re: Where to start - putting it back on the road

#159 Post by PaulGreen » Sun Dec 16, 2018 3:07 pm

I picked up a compression tester on the way home from work today. There's a lot to be said for consistency, but consistently bad is less useful.
I was horrified to see 45 psi across all cylinders.
They're all EXACTLY 45 psi, which makes me suspicious of the tester. I'll try and find another petrol engine to check it out. But it looks like we're looking at another top end inspection/rebuild?

Out.
Paul.

PaulGreen
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Re: Where to start - putting it back on the road

#160 Post by PaulGreen » Sun Dec 16, 2018 3:36 pm

Forgot about the "wide open throttle" bit.
I'll be back.
Fingers crossed.......

Paul.

PaulGreen
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Re: Where to start - putting it back on the road

#161 Post by PaulGreen » Sun Dec 16, 2018 3:47 pm

Sheeeeeiiiiiitttttttt!!!!!!!!!

Still 45 psi

Paul

lost1750GTV
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Re: Where to start - putting it back on the road

#162 Post by lost1750GTV » Sun Dec 16, 2018 3:55 pm

it's pretty hard to achieve uniformly low compression.

unless you were very careful about doing something consistently wrong, but short of making your own really thick base gaskets ....

PaulGreen
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Re: Where to start - putting it back on the road

#163 Post by PaulGreen » Sun Dec 16, 2018 4:09 pm

No, base gaskets were part of a kit, I don't think they were genuine, I can't remember. From Yambits I believe.

When you say it's difficult to get consistently low compression are you suggesting that the reading may be wrong? Or my engine's fooked?

Paul.

silverstrom
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Re: Where to start - putting it back on the road

#164 Post by silverstrom » Sun Dec 16, 2018 5:51 pm

Unless you have made the same monumental mistake in all 4 cylinders the gauge has to be the reason for the low reading. Screw the tester into the plug hole ensuring an air tight fit, then kick and kick until you get the highest reading. If you've done that and after many kicks it doesn't read more than 45 PSI, try another tester. If you still get 45 PSI with a different tester you'll be back into the top end to have a look around. Rings, ring gap, piston to bore clearance, etc.

I hope the head gaskets are genuine Yamaha. Aftermarket head gaskets will leak.

And for what it's worth, I have never seen much of a difference with wide open throttle or closed throttle when compression testing.

PaulGreen
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Re: Where to start - putting it back on the road

#165 Post by PaulGreen » Sun Dec 16, 2018 7:26 pm

As I mooched around on the internet looking at another rebuild project, I think I'm fairly sure that I used non gem gaskets. I think I used vesrah(?) gaskets.
I'm going to struggle to get hold of another comp tester without buying one, and the only other petrol engine I've got access to to test the one I bought us my wife's A class Mercedes. And to get access to the plugs on that you need to be an 8 year old contortionist!
Having said that, my options are limited, so I'll get the yoga mat out and have a go. When it stops raining.

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