Picture Attachments Fixed? (18 Feb 2023)
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RT1B compression .
- shyted
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RT1B compression . was created by shyted
I said about lowering the compression with the fitment of a thicker copper gasket .
I bought one from a manufacturer in Arizona after messaging to and fro for a few days.
The thickest one available to be cut from sheet without making it susceptible to splitting.
I fitted it as directed to the letter.
Also,i raised the needle by two notches on the carb.
The result, lots smoother running,you can start it without MX boots on and starts first kick every time hot or cold.
The thing is,there's no noticeable performance loss,in fact it's more responsive. The pinging seems to have subsided and the horrible overrun is loads less.
Still room for further improvement though. I have some ideas to try over winter.
Just so you know it works.
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- AirborneSilva
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Replied by AirborneSilva on topic RT1B compression .
1976 DT400C
1981 DT175H
1972 DT2 250
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- 1971DT250
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- Sneezles61
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Sneezles61
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- msavitt
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- automan
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Replied by automan on topic RT1B compression .
Makes it lean and knocks is common.
cliff
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- MarkT
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Replied by MarkT on topic RT1B compression .
(Years ago I came across a video with a camera pointed at the exhaust flange and with every "bang" on decelleration you could see a puff of smoke and the pipe bounce away from the engine slightly.)
Engines with a better seal at the head pipe... like some of the later Yamaha's with a solid flange holding pipe to head... seem less likely to do this... so fresh air getting drawn into exhaust from leaky connection at the head pipe could contribute to "pipe bang" in my experience.
There are also some theories that the ultra rich mixtures from misfires and the poor scavenging can result in very high compression pressures (fuel doesn't compress so a few cc's of extra fuel will raise compression pressure). With non-uniform conditions in the chamber a "pocket" of not-too-rich mixture preignites... this type of "pinging" is usually accompanied by a brief surge of acceleration along with the "ping" in my experience.
The engines larger than 250 seem more far more likely to have the "surge-ping" which is probably preignition. I'm not sure anyone knows for sure.
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- Sneezles61
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I’ve just got used to pulling in the clutch… but that’s road riding…
Sneezles61
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- Ht1kid
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- RT325
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