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For the record, this is what detonation looks like

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I found this one in my old photobucket account.  This one melted down at about 100 MPH in an RD400.  The battery was also dead so when the motor locked up the headlight went out, and of course this was pretty late at night so I was skidding down the road in absolute darkness.  Fortunately the motor freed up before I high sided or hit the median and after a few minutes of pushing I found that it was able to restart and ride home on the remaining cylinder.

 

DET.jpg

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On 11/16/2017 at 11:25 AM, turbo dan said:

I found this one in my old photobucket account.  This one melted down at about 100 MPH in an RD400.  The battery was also dead so when the motor locked up the headlight went out, and of course this was pretty late at night so I was skidding down the road in absolute darkness.  Fortunately the motor freed up before I high sided or hit the median and after a few minutes of pushing I found that it was able to restart and ride home on the remaining cylinder.

 

DET.jpg

Yep, that is a "worst case" picture of two stroke tuning!

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54 minutes ago, GlennRay said:

Yep, that is a "worst case" picture of two stroke tuning!

Never owned an RD huh???

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Just now, MentalGuru said:

Never owned an RD huh???

Nope, only single cylinder YZ-125 and YZ-250s.

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I never owned an rd. I take it this was common?

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19 minutes ago, GlennRay said:

Nope, only single cylinder YZ-125 and YZ-250s.

Imagine them being air cooled and operated at sustained part throttle, closed throttle and full throttle high speed high rpm highway use for miles on end.   The difference is night and day. 

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Both of mine were air cooled.  They got operated all over the throttle range.

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Just now, bodge said:

I never owned an rd. I take it this was common?

Depends on how they were ridden.  If the oil injection was removed that didn't help piston life either.  If it wasn't removed then at high speeds the engine mainly saw a air/ oil mixture with hardly any fuel.  Guess what the octane rating of oil is and if it burns off as quick as premix does.

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3 minutes ago, GlennRay said:

Both of mine were air cooled.  They got operated all over the throttle range.

In top gear at rpm for say stints of 50 miles or more at a time?  I've ran an RD400 for over 150 miles with an average speed of around 85mph.  It holed a piston a week or so later.  The RD350 that was with us holed one at about the 80 mile mark at about 110mph.

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I think the problem with this one was too much compression and imprecise jetting and timing.  And the motor was loose enough that I couldn't quite hear the det over the various other mechanical noise.  I could have throttled back and saved the motor, they don't just do this spontaneously. 

The stock ignition requires setting timing for each cylinder individually, and of course had no advance or retard ability.  I bet that burned down a lot of motors. 

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How was the rz350 vs the rd? Same problem or did the liquid cooling solve it? The rz is the same as a banshee motor right?

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Just now, bodge said:

How was the rz350 vs the rd? Same problem or did the liquid cooling solve it? The rz is the same as a banshee motor right?

The RZ had power valves unlike a Banshee and a better ignition system then an RD did.  I've seen some RZ's with 10,000 miles on original pistons.  They were great bikes, wicked fun too.

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