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Makotosun

Air Coolled Two Stroke Paranoia.

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Replied by shyted on topic Air Coolled Two Stroke Paranoia.

Hahaha, looks are deceiving .
BIN? You could have drawn a lottery win if you sold it on ebay. Some people re fit them to RD 250 & 400s and what have you and for what they are they pull cash. If i'm honest i would say bin too. You learn from that the first time they jack in.
PJME are pretty good and keep some pretty fragile engines ( Aprilia RS 125 ) operational.
04 May 2023 15:07 #21

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Replied by Tinkicker on topic Air Coolled Two Stroke Paranoia.

I swear that bike is cursed. I know that the original owner back in 1979 had an accident on it and it was never ridden again. I am starting to think that he was killed on it. It is getting ridiculous.

Barrel has been away at the motorcycle engineering shop having a new liner made and fitted since the beginning of the month, and is expected back around the end of June.

To save a mess from any oil dripping from the two stroke oil injector line whilst disconnected from the carb, I put an aerosol paint can cap under the end to catch any drips.
It has been sat thus for a month with just a couple of drips in the cap and a full oil tank. You can see the bike clearly from the sofa, displayed at the other side of a glass patio door, not six feet away and as it is my baby, I gaze at it often.

Came home from work yesterday and noticed the oil tank was empty... It had suddenly dumped its entire contents over the conservatory floor in the space of less than 24 hours.

Nothing has changed, the bike has not been disturbed and no one has been in there.

A WTF moment.

Now wondering if a faulty, intermittently sticking check valve has contributed to the demise of the cylinder, although it normally uses between a quarter and a fifth of a tank of oil to one tank of petrol, so it seemed to be getting plenty of oil and the piston is showing no signs of wear or score marks.

Oil pump rebuild kit and check valve kit is winging its way to TK towers as we speak.
26 May 2023 04:38 #22

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Replied by Gr8uncleal on topic Air Coolled Two Stroke Paranoia.

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26 May 2023 04:44 #23

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Replied by MarkT on topic Air Coolled Two Stroke Paranoia.

Yes 

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The only thing that comes to mind is checking the oil tank vent hose...  on US models it runs uphill along the frame under the fuel tank.  If pinched or blocked oil tank might build pressure?
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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26 May 2023 05:07 #24

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Replied by RT325 on topic Air Coolled Two Stroke Paranoia.

Blimey it's all happening at your place. Says a lot for premix but pumps are generally reliable except those light spring & ball on the pump outlet get stuff caught there.
Re-sleeving the cylinder seems extreme & expensive when you can go to 1mm over in 4 steps.
Hope she starts behaving when all this is sorted.
Talking Heathrow [your motor pic a few posts back] I flew into Heathrow in an A380 about 6+ years ago & couldn't see a damn thing.
Pilot said gotta circle for a while & wait our turn. Then [we're going in] [hope he means landing lol]. Couldn't see the runway until the wheels touched . Amazing aircraft though--Amazing that much weight gets off the ground.
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Last edit: 26 May 2023 05:17 by RT325.
26 May 2023 05:08 #25

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Replied by Tinkicker on topic Air Coolled Two Stroke Paranoia.

Yes.  When I bought the bike it was on premix.  The previous owner could not manage to get the oil pump working.

I put a piece of clear tube on the pump and noticed that oil was oscillating back and forth instead of heading for the carb and thought that the check valve was stuck open.  Put a syringe with oil in it at the end of the line, removed the bleed and backflushed the valve.  Job done.  Pump was now pumping.

Feeling smug, I changed the pump shaft seal only.  What I should have done was stripped, cleaned and rebuilt the pump. 

I am good at being wise after the fact.


 
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26 May 2023 08:09 #26

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Replied by Yamfan on topic Air Coolled Two Stroke Paranoia.

If you have a DT175 with a trashed cylinder, why not buy a new one from ebay? Lining is never a good idea, if it can be avoided, and the cost may well be higher than the new cylinders from ebay. If the PO was using pre-mix, the oil pump is probably toast?
26 May 2023 10:12 #27

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Replied by Tinkicker on topic Air Coolled Two Stroke Paranoia.

1. You cannot get 1978/9 design cylinders on ebay. My bike is of concourse condition and originality is everything. RT has it right, yes I could have had it rebored to 1mm. But would a concourse bike with less than 2000 miles on the clock be expected to be at max oversize?  As an engineer , i am anal about such things.

2. The oil pump is fine, it is getting, and should have had previously, a full rebuild with new seals and a good clean out.
The ex senior motorcycle techie of an owner made a serious balls up in not doing this before and has been kicking himself up and down the yard ever since this came to light.

3. The barrel has been sent to a reputable firm with a solid foundation in relining cylinders.  They are considered the best in the country.
Last edit: 26 May 2023 15:18 by Tinkicker.
26 May 2023 15:15 #28

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Replied by RT325 on topic Air Coolled Two Stroke Paranoia.

1mm is max. What's on now .75--goes in 10 thou steps up to 1mm.
Sorry not trying to change your plan--just thinkin out loud.
Wiseco--seizco go in half mm steps in old fashioned wiseco.
What piston is your used one.
Last edit: 26 May 2023 17:18 by RT325.
26 May 2023 17:17 #29

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Replied by Tinkicker on topic Air Coolled Two Stroke Paranoia.

Originally the bike came with a totally unworn, but deeply rust pitted bore because of it being stood for 40 odd years. The piston had come to rest some 10mm below tdc. There were bands of very deep pitting where the rings were.

They may have cleared at .25 but it looked to be too close to call.

Rather than supply a new TKR piston at 1st over, I decided to jump straight to .50 to be sure. I did not want to find the machine shop eventually had to bore it to .50 and then be supplied with a cheapo ebay chinese piston in replacement for my TKR.

After measuring the bore just above the ring of ports, I found the cylinder to have been bored, or subsequently honed barrel shaped by .25 mm from top and bottom measurement. A quality mercer cylinder gauge was used for the measuring.

So it is likely that third over is not an option, so we are looking at max oversize.

I could have had it bored to max oversize, but on a bike with less than 2000 genuine miles, it did not sit well with me. The damage should be corrected and be put back in a state that it was just before it was parked up way back in 79. Hence going back to std.

I view myself as a custodian of the vehicle and have built it to last another 40 years, although it seems the bike is fighting this.  I never knew a rebuild with so many "teething problems".

Ran 70 odd off road bikes and quads at a very large yamaha motorcycle activity centre for young offenders that I used to work for in a previous life, and considering expected service lifetime being around just  9 months between complete to the last nut and bolt, stripped down to the crank overhauls, and just 3 months between full suspension stripped off and rebushed major services,  I was rebuilding them on a weekly basis.  You could say my team was run ragged.  Very stressful job.  A set of front pads lasted a week, chains and front sprocket two weeks.  Rear tyre lasted three.  Full safety inspection and minor service every day.
Such is the life of offroaders running 6 hours a day, 7 days a week in deep mud, by naughty boys who were more like animals in a human skin than people.

Never had one fight back like this un though.  It is like it does not want to be finished.  
 
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Last edit: 27 May 2023 01:19 by Tinkicker.
27 May 2023 00:49 #30

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