Well... this was not how my night was supposed to go. Didn't have my camera on or I would have shown you the actual moment. But, I was riding home from the girlfriend's house. She's around an hour from me if you take the freeway. The ride to her place I plotted out on surface streets and got there in just under 2 hours earlier today. It's late, I'm tired and its getting dark. So, I decide to forgo the surface street fiasco's and just take the freeway. All was well for around a half hour (minus the fact that 75mph on this bike is torture, and I was fully aware of this lol).
A mustang cut in front of me and slowed down as a car in front of them braked. I rolled off the throttle pretty heavy and snapped it back open. That slow... methodical melting sound started and I immediately pulled the clutch in. Motor shut off right away as was expected. I managed to make it across 3 lanes and coast to a stop. A nice and soft kick check confirmed. Solid as a rock. Like a Chevy.
After the initial whoopsies, and choice words, I began pushing my dead soldier along the side of the freeway. About 300 feet or so before I tried the kicker by hand. Well, it rolled over... tight, but rolled over. Waited a few more minutes and kicked it for real. She felt ok. Fired it up and happened to be on the 11 mile exit. Rode 35 to 45 mph home with the deafening slap of the right side piston. But, I do have to say the bike did indeed make it home under it's own power. Ran on both cylinders too.
I'll check it tomorrow. But, I have a feeling I ran it lean. It was around 70F. 200 mains, Dave F, 3rd position.
Sorry to hear this Striker. Is the bike on pump or premix?
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:bang: Not a good feeling.
Yikes. Rebuild and ride
I hate that for you but it has happened to almost all of us at one time or another. We know your Fall/ Winter project and it will be back bigger and better than ever.
That is a bad/expensive feeling. But seems like riding it overcomes all that when they run right.
Bike is indeed on the pump Arrow. As it was prone to eating oil and fouling plugs heavily, the pump cable was delayed 2mm or so. I rebuilt it when I put the engine together. Rebuilt as in new internal/external seals. Did not replace ball springs etc.
Please check if the minimum stroke is still within specification.
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Quote from: Striker1423 on September 13, 2020, 08:16:23 AM
Bike is indeed on the pump Arrow. As it was prone to eating oil and fouling plugs heavily, the pump cable was delayed 2mm or so. I rebuilt it when I put the engine together. Rebuilt as in new internal/external seals. Did not replace ball springs etc.
Normal oil use is approx 1 litre of oil to two tank full's if fuel, but depends very much on how you ride.
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sounds like you built up a decent amount (more than normal) of heat in the motor on the 75 mph run, and the quick stab added just enough to stick it. where were you throttle wise? 1/2, 3/4 for the steady run? that's where i'd look. also, whats timing set at?
this is why it can be tricky on bikes (not nec yours in this case) with curves. if you are at max advance at cruise, it creates a lot of heat. therefore, sometime seven with HPI setups or the like, its better to be a bit more conservative with initial timing.
sorry this happened. it always sucks.
I could be wrong, but I'm guessing that the closed throttle part of the story was the cause.
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it may have been the tipping point , i agree, but that heat was there already, so it must have been on the edge.
could be that, the main, the timing, the needle, etc.
forensics time.
So, from what I remember, I was cruising at 75mph (within variation of 70 to 80 at times). My RPM gauge doesn't work, but the throttle was around 1/2 up to a bit over 1/2 to pass, etc. 75mph puts this bike inside the powerband and it stays there. It's very hard to hear what the bike is doing at that speed, but all seemed ok. I was on the freeway for roughly 40 miles.
When I rolled off the throttle, I didn't close it fully, I'd say I dropped around 1/4 throttle. Just enough to slow from 77 or so mph down to 60. It began to slow rapidly and sputter right before and as I was rolling on the throttle steadily back to half. That's when she gave up.
Let us know what you find with the minimum stroke.
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Quote from: Arrow on September 13, 2020, 09:43:09 AM
Let us know what you find with the minimum stroke.
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The minimum stroke I see is opening about 0.35mm at idle. Turning the wheel by hand ( as the book states to do) isn't opening the pump. But, it appears to be pumping correctly at idle.
0.35mm is big. I'm wondering why the priming wheel doesn't turn the pump over? Post a video of this, if possible.
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sounds like the plunger isn't returning.
A photo would be most useful here, a short video even more so....
Striker, Just to confirm we are not getting crossed wires here, can you confirm the pump has the white plastic thumb/priming wheel on the back, or not? Sometimes people refer to the pulley (that has the cable attached) as the 'wheel'.
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After I rebuilt my pump, it wouldn't stroke using the wheel. I found that the gasket for the pump housing is thicker than oem and takes up the clearance, requiring more shims. To verify, remove the plate at the end of the shaft(where you check clearance) and then see if the pump will operate by turning the wheel.
Quote from: JB Weld on September 13, 2020, 08:48:39 PM
After I rebuilt my pump, it wouldn't stroke using the wheel. I found that the gasket for the pump housing is thicker than oem and takes up the clearance, requiring more shims. To verify, remove the plate at the end of the shaft(where you check clearance) and then see if the pump will operate by turning the wheel.
This would be rectified before committing the pump to service - surely? Striker states 0.35mm.
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I seized my TDR under roughly the same circumstances, so I feel for you. 75mph to locked solid is no fun at all.
Your in the best of hands with pump guru Arrow, best of luck.
Needle too lean maybe?
Here's a video explaining what I did and how I had to check it.
https://youtu.be/eBsFIeQ1xrw
There is quite a bit going on there! I can't explain why there is movement when the motor runs, but none when you turn the wheel. I simply have not seen that before. First time for everything I guess, but something is not right for sure.
Please replace the cable tie on the inlet pipe with the correct wire clip. Where the block is there is a gap, not good. Also the retainers on the outlet pipes do not fit all the way round the pipes. This is bad news as the motor can pull air through those joints, due to a constant vacuum in those pipes when the motor is running.
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Can you try another thing please? Start the motor and hold the pulley right down towards the main body of the pump, so its on full stroke. It should be observed that on the inward stroke the shims pretty much contact the end of the top casting. Is this so, or is there a gap? If the latter, how big?
Again, a short video would help.
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the spring under the cable pulley isnt seated in the body either. or at least sure looks that way. :umm:
Quote from: m in sc on September 14, 2020, 10:57:40 AM
the spring under the cable pulley isnt seated in the body either. or at least sure looks that way. :umm:
Those "early" pulleys have a much bigger PCD where the cable runs, and two fitting points. One is below where the cable runs.
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look at the spring un-tensioned by the cable.
The spring is returning the pulley, as far as I can see. Its a pattern spring, by the way.
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just looked odd to me. but i defer to your expertise on the pump.
i still think its the tune that caused the seizure. :twocents:
Thanks. I don't disagree with you, it could well be the tune. If we rule other things out, the tune may still be with us.
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Post some pics of the piston, particularly the crown and underside.
The spring was a new replacement as earlier on the 250 top end I had a return issue (it was cable related not the spring fyi). That was as far down as the spring would go into the pump body. I wound it as tight as it would allow the pump to open. Was a pain, but it has never let go.
As far as the pump is concerned, I will do as Arrow asks. As soon as I get footage I'll let it cool and tear the right head off and see the piston.
I should note as I hadn't mentioned before. That when I gave the bike full throttle on the freeway, from 3/4 to the top, the bike was no longer building steady power. To me that indicates lean, but I'm sure the piston will tell the tale.
Thanks for the update Striker. The pattern spring has longer ends than the Yamaha spring. It can only fit (as all pulley springs) with about 1/4~1/3 turn of tension. If not the pulley will not rotate to fully open.
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Am I correct in saying, your pump has no gasket fitted between the two castings?
I would like to actually see this pump and sort it properly for you. But like most things in life, there is always a down side.......
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Quote from: Arrow on September 14, 2020, 09:29:09 PM
Am I correct in saying, your pump has no gasket fitted between the two castings?
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You mean the main body of the pump, in the middle of it? When I replaced the seals I followed the WellaRD guide on the aircooled RD forum for the pump. The rebuild kit I purchased only had the new seals, screws, and the square gasket for the pump cover. It did not come with new check balls, or springs. This was 2 years ago so I don't remember if a gasket was on the main body of the pump or not. If it was, I believe I would have tried to save it.
Here's the new video.
Thats ok.
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Ok, so the initial look revealed what looks to be a four corner seizure. Still have to disassemble the carb setup to pull cylinder. I'll also pull the left side just to be safe.
(https://i.imgur.com/Y8YTwBo.jpg)
(https://i.imgur.com/xEsSt8o.jpg)
(https://i.imgur.com/fEjrGJd.jpg)
(https://i.imgur.com/3IIIugt.jpg)
Under the crown will tell the story, but yeah, i think heat. just enough.
Here's the piston crown.
(https://i.imgur.com/kOF0GMP.jpg)
EDIT:
Here's the piston sides too.
(https://i.imgur.com/XvE3xvm.jpg)
(https://i.imgur.com/BMSIhbn.jpg)
Doesnt look lean, the piston is washed completely clean. But it did get hot.
Rich mixture could have been just enough to keep it cool enough to stop melting until you got off the gas.
Mark looks like he was correct with something in the ignition
I set the initial timing with the dial indicator to 1.8mm on the Vape ignition. I found an old Craftsman timing gun on Ebay and bought it. It worked well...sporadically, but it looked OK once functioning. However, I was having trouble with the ignition rotor slipping. I thought I rectified it by heating the rotor and re-seating it, but perhaps the timing moved? If the rotor did slip, wouldn't it only retard?
Also, the left side piston and cylinder looks just fine. A bit oily as it should be, with no real discoloration. Both heads look identical too.
weird it was on the right. any signs of a slight head gasket leak? inspect the gasket very closely, look for a line across it, even a thin one.
def doesn't look oil related.
Im not going with timing either, the domes would look different. It got just hot enough just quick enough to expand that piston just enough to stick.
you know, it might even boil down to the bore clearance was just a hair tight on that side, that simple. :twocents: everything else looks correct of the headgasket checks out.
It looks like the head gasket may have started to leak out the front side. How much run time since it was bored? Could it be that side was just a touch too tight? Is that a forged piston?
Here's a few more. I should also note, that the spark plug hole was repaired with a timesert. Well, at least a similar thread repair. I always have dark threads on the spark plugs on this side. But, never noticed any loss of compression. Perhaps it leaked there? May be the culprit.
Runtime, just over 2000 miles on it. First time on the freeway for over 10 miles. Wiseco pistons.
(https://i.imgur.com/YwVwV2O.jpg)
(https://i.imgur.com/14sECvC.jpg)
(https://i.imgur.com/2nCsvwT.jpg)
man that plug is oily.
Quote from: 1976RD400C on September 15, 2020, 03:47:23 PM
It looks like the head gasket may have started to leak out the front side. How much run time since it was bored? Could it be that side was just a touch too tight? Is that a forged piston?
looks like it may have had a slight leak, under gasket, at arrows. decel may have sucked air in and bam. whgat does underside of gasket look like and cyl?
Here's the underside of the gasket and the cylinder.
(https://i.imgur.com/dyG6lH8.jpg)
(https://i.imgur.com/N05Gtpq.jpg)
I did use 3 coats per side of copper spray a gasket.
This dark area, perhaps?(https://uploads.tapatalk-cdn.com/20200915/42d99b4ccdb0c464f1cd1e85ca8ec949.jpg)
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Possibly. I don't really know what to think. Maybe the bore wasn't actually correct.
These are simple bikes, but things seem to get more complicated some 1/2 Century after they were made. Thankfully/hopefully, they can still live.
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Piston top and plug show the tune is too rich in general. Oil pump appears to be working. No sign of detonation.
I Also suspect the Piston/bore clearance was too small for the forged Wiseco. It didn't fail earlier because the tune was so rich that it prevented complete piston expansion, until the freeway did it.
Does the other piston show sign of wear on 4 corners?
Quote from: Alain2 on September 16, 2020, 05:57:35 AM
Piston top and plug show the tune is too rich in general. Oil pump appears to be working. No sign of detonation.
I Also suspect the Piston/bore clearance was too small for the forged Wiseco. It didn't fail earlier because the tune was so rich that it prevented complete piston expansion, until the freeway did it.
Does the other piston show sign of wear on 4 corners?
No. The other side was fine.
Been there-done that.
Cold siezure on a new build.
Minor, and fired back up. to limp it home. All 3 jugs/pistons were still perfect!?!
Hi guys! Newbie here.
cliff
Standard mode of failure on a 2 stroke. Forget the piston wash interpretation for a moment because it ran home after the meltdown so we can't really tell too much. Typically, a lot of carbon on the head or piston indicates a lean mixture and a clean surface with more washed than carbon tends to indicate rich, but we can't say too much because we have no idea if that carbon was built up when it was run hard or tootling along.
What we can tell for sure is that the piston expanded to the point that it had minimal to negative clearance and that's why it had a 4 corners seizure. There's no obvious signs of detonation or oil film breakdown except on those 4 corners.
The causes are usually too little clearance or more likely, it's lean on the needle jet. Most of us know how to check main jet color on a plug and for slow speed running but if it's lean on the needle, all we do is open the throttle a little more. And that kills a two stroke cruising down the highway at steady throttle/rpm/speed. Motor gets hotter and hotter and it either starts to detonate or it nips up like that one.
We had a TD3 that did that too many times at Daytona at full tilt and it turned out to be a minor air leak in an inlet manifold.
Do a leakdown test and see if there's a slight leak anywhere. Follow that with checking piston to bore clearance or go slightly loose next time and if all that looks good raise the needle one step.
Good things to note Teazer. She's currently in boxes and a thousand pieces. If I'm overhauling it again I'm doing it up real pretty like.
Striker, I wish I was nearby and could measure the pistons and cylinders. Regardless of what really killed them the measured clearance is good data points for RD riders. If its closer to .002" than .003" then I would say it didn't leave a safety margin and part of the problem. You could clean the aluminum from cylinders with acid and hone a couple tenths more, fit new pistons and have that part fixed. If it didn't scatter aluminum into the crank I would run it if all else looks good