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PostPosted: Thu Sep 05, 2019 7:47 pm 
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On the street

Joined: Mon Aug 10, 2015 8:43 am
Posts: 16
Country: US
Bikes owned: 75 Suzuki GT250, 74 Kawasaki H2
Hey guys,

I recently posted a question about my oil pump arm not returning correctly. http://www.suzuki2strokes.com/forum/viewtopic.php?f=9&t=14013&p=173500#p173500

Here's the full story. Two years ago, I was riding my restored GT250 back from work (a short, 7 mile commute with stop signs, stop lights, etc). At this time, I had about 600 miles on the restored bike - all the kinks ironed out.

So, about 1/2 way home, I noticed the bike was getting a bit fussy...it didn't seem to idle right at stops. One of the cylinders wasn't firing quite right. So I held the throttle open a bit (that seemed to help). I got a few blocks from my house, and now one cylinder was basically dead. I had to ride on the side of the road because I couldn't get going fast enough for the 35 mph traffic.

I chalked it up to a carb float getting stuck. I parked it in the garage, thinking I'd take a look at it whenever (this was fall in MN).

The next year I picked up a 74 Kaw 750. Totally my focus. The GT250 sat.

This year, I found an amazing deal on a hold-over (non-sold) 2015 CB100R (like, almost 1/2 off sticker price). I had to have it! The wife said, "you can buy it, but you need to sell one of your bikes." Done!

The GT250 was the gal. After the CB1000R was sitting in my garage, I pulled out the GT250. Remember, I thought a carb was just being stubborn. I fired it up - and I could clearly see it was the right cylinder not firing. I shut her down. Cool, I'll just pull the right carb off. As I was removing the two nuts on the carb, I happened to look down and noticed the oil pump cable looked a bit off. I grabbed it, and it was loose! F!

I quickly removed the oil pump cover, and to my horror, the cable was completely detached from the oil pump arm.

My mind raced. This was the reason the right cylinder stopped firing! I thought, while riding home, the cable was detached, and I burned up the rings enough that compression was lost. And I thought, thankfully I didn't lock up the engine - I surmised that my synthetic two-stroke oil had saved the engine.

I hooked up my compression tester. The left (good cylinder) read 120 psi. The right (bad cylinder) read 90 psi. I checked the spark on the right cylinder - she was lighting up. Not good, as 90 psi is not strong enough compression. I sprayed WD-40 into the right cylinder, tried it again, then it got to about 120 psi. This was my first mistake. I should've trusted that value.

However, with the oil pump cable loose, and my first reading of the right cylinder, I was certain that the right side rings and/or cylinder was compromised. I even did some crude micrometer measurements - and they all came back as "marginal" in respect to the hayne's manual.

So, I popped off both cylinders, searched (and found) a couple of 0.5 oversized pistons (and rings), and brought the cylinders/pistons/rings to a great machine shop near me (bill bune).

Sunday, 9/1/2019, I installed everything (new gaskets, the whole deal). Started the old gal up, same problem! Seriously? I just did all of this, and the right cylinder was DEAD. I threw some gas into the right spark plug hole, nothing.

I sat there, in my garage, 6pm, defeated. So I did the old 3 point test in my head. I have gas, I certainly now have compression, and I thought I had spark (I did).

I was just about to go back into the home and have a beer. Then I thought, why not take off the left-side ignition cover? I did. Then I started the bike (firing on the left cylinder). I looked down, and saw the right-side points firing like lighting bolts. I looked back to my hayne's manual, and it basically said if you see this, your condenser is bad.

The next day (labor day), I dug out my old right-side condenser from the rebuild (I save everything). Installed it, and sure enough, the gal was running perfectly!

So, in the end, I spent $250 on new pistons, rings, gaskets, and a bore for each cylinder...when it just needed a $10 condenser.

The oil pump cable was probably disconnected when I was fussing around with the throttle when the bike was not running (after the ride home).

So, as promised, a story of a bunch of ill-timed unfortunate events that lead me to believe something that wasn't correct. It still torques me that I had my GT250 bored from original to .5 over (it's only got 4200 miles on the clock).

At any rate, I had to share this story with folks that would appreciate it!

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http://www.machinesofman.com

75 Suzuki GT250, 74 Kawasaki H2 750, 82 Suzuki RM 125, 00 Kawasaki KX 250, 15 Honda CB1000R


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PostPosted: Sun Sep 08, 2019 2:12 pm 
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Expert racer

Joined: Mon Dec 01, 2008 2:52 am
Posts: 1194
Location: Manchester, UK
Good story! We've all been there to some extent - chasing a problem and missing the real cause. Even with the oil pump cable detached, the pump still delivers oil to the crank and cylinders, not enough for fast open road work, but probably enough for town riding.

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1976 GT380 - wounded by me, and sold on
2006 SV650S - killed by a patch of diesel and a kerb in Feb 2019
2017 SV650 AL7 - naked and unashamed


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PostPosted: Sun Sep 08, 2019 4:34 pm 
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On the street

Joined: Mon Aug 10, 2015 8:43 am
Posts: 16
Country: US
Bikes owned: 75 Suzuki GT250, 74 Kawasaki H2
Thanks Craig380,

When I took the right cylinder off, I ignored the fact that it looked clean, the rings looked clean - no scoring. I'm still kicking myself!

One of my weaknesses (when it comes to engines) is the electrical aspect. I find it tedious and annoying. So, when I saw spark (with the spark plug) - I dismissed that as being a problem. I really wasn't paying attention to the fact that the spark was not a nice, crisp blue (it looked yellow and seemed to flash erratically).

I fully went down the red herring path - thinking my previous experience gave me the authority to diagnose a problem that wasn't there (as you eluded). I'm throwing out my mistake so a future guy (like me) doesn't get too cock-sure about the real cause.

Mark

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http://www.machinesofman.com

75 Suzuki GT250, 74 Kawasaki H2 750, 82 Suzuki RM 125, 00 Kawasaki KX 250, 15 Honda CB1000R


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PostPosted: Tue Sep 10, 2019 1:04 am 
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Expert racer

Joined: Mon Dec 01, 2008 2:52 am
Posts: 1194
Location: Manchester, UK
Oh yes. Ask me about the time that I checked the timing & plugs, cleaned the breaker points, disassembled the fuel tap, and removed the carbs for cleaning to try and solve a mysterious but loud popping / banging on neutral throttle or deceleration at 4,000rpm in any gear.

It sounded bad. I found nothing, despite weeks of investigating and hair-pulling. Then I tried my springy drain-clearing snake, poked it up the centre expansion chamber and gave it a good rodding-out. Noise disappeared completely. It was carbon build-up where the chamber was welded to the header. It had built up in a ring inside the pipe, restricting the ID and causing an exhaust resonance in the belly of the chamber, which made the banging noise.

It's why we love these bloody 2-strokes :wth: :mrgreen:

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1976 GT380 - wounded by me, and sold on
2006 SV650S - killed by a patch of diesel and a kerb in Feb 2019
2017 SV650 AL7 - naked and unashamed


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PostPosted: Tue Sep 10, 2019 3:15 am 
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To the on ramp

Joined: Fri Aug 11, 2017 7:09 am
Posts: 400
Country: england
Bikes owned: several gt250 ramairs
my favourite trick was finish rebuilding an engine, fit it, all connected up, turn it over on the kickstart a couple of times and after a quick wipe over with a rag, retire to the pub - or bed :D after 10 minutes or so, start questioning "did i put the outside piston circlips in"? i'm sure i did. did i? i've stripped the engine down the next morning and they've always been fitted :D it can really give you paranoia. hours of work for nothing, except peace of mind :lol:
cheers, dd.

_________________
GTS250 road registered. TS250 engine, Ramair frame.
GT250 big bang road registered. Both pistons fire the same time. USD forks.
GT285 road registered. Overbored - 58mm and TS125 +2 pistons fitted.
GT10 road registered. '65 T10 engine, GT250 frame.


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PostPosted: Fri Sep 13, 2019 9:04 pm 
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Expert racer

Joined: Tue May 18, 2010 5:38 pm
Posts: 1447
Location: New Hampshire
Country: USA
Bikes owned: Suz, Yam, Honda, Kaw.
I have acquired several old toys from others due to condenser. Some condensers are staked (if the right word) in place, no screw to bond to ground. Person bring bike/snowmobile/etc. to a mechanic to have points changed and they never due the condensers (some lie about it) since staking is a little harder to do or do correctly (get loose). After some hours of running same issue returns haunts the owners. Confused, not wanting to spend anymore money it sets until someone takes the nightmare off their hands. :ssh: Aah the good old days... been a while since points were replaced with solid state. Usually I hear it back fire out exhaust cluing me in about such a problem starting to occur.

Also those dang aftermarket ones suck!. OEMs condensers only.

I have never had one of my Suz oil injections cables break (knock on wood), but I have had a few fail on Yamaha (other makes too) , maybe just my luck.

To this day I still run ~1.5 oz of oil per gallon in my gas tank on all my two stroke oil injected engines as insurance.

_________________
Current Bikes
74 GT250 (T350 upgrade),
76 GT250 (T350 upgrade),
71 T350,
70 T350,
74 GT380,
75 T500,
73 GT550,
75 GT750,
72 Yamaha DS7 (R5 upgrade),
77 Yamaha RD400 (Daytona Cyls),


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