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1973 Yamaha DT-250 making terrible noise

27 Jun 2020 13:36
Yamaha dummy
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1973 Yamaha DT-250 making terrible noise #1
Hello all! I’ve had bikes since I was 9 yrs old and now have a dt-250. Been a great bike to mess around on back roads. But now any bumps or varied terrain she is making a clunking sound. almost like she’s missing or a piston ring could be bad? Seems to be fine on gear oil. Also, how do you tell if oil injection is working on these?

Thank you!

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27 Jun 2020 14:08
Jcummings2772
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1973 Yamaha DT-250 making terrible noise #2
What does it sound like when it’s simply sitting still?
Or on smooth terrain?
Clunks and bumps from bouncy terrain simply sound like a loose bolt or bolts somewhere

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27 Jun 2020 14:20
Yamaha dummy
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1973 Yamaha DT-250 making terrible noise #3
I tried to replicate the sound with it off. Hoping it to be shocks. Nope. When she is in idle or cruising on our flat dirt road, no clunk or bad sound. The second it’s pushed up a bumpy incline makes a horrible clunking Almost like it’s skipping gears or chain but sounds to be coming from under my seat and in the motor. Or gear/clutch. Really puzzling.

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27 Jun 2020 14:22
Yamaha dummy
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1973 Yamaha DT-250 making terrible noise #4
But it also is slipping and seems to not engage while going on bumps and uphill. I’d upload a video if i could.

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27 Jun 2020 14:43
The Crafting Rider
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1973 Yamaha DT-250 making terrible noise #5
maybe a worn clutch basket? sounds to me like the clutch plates may be smacking against the basket. over time the fingers develop grooves and allow play.

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27 Jun 2020 15:09
HouseofEnduro
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1973 Yamaha DT-250 making terrible noise #6
Check the front sprocket for excessive wear, I see the rear has been replaced so possibly the front is original with worn teeth and allows chain to skip under load.
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27 Jun 2020 15:14
Yamaha dummy
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1973 Yamaha DT-250 making terrible noise #7
Could be. How do i access them? It makes the sound as i rev like I’ll do a quick rev while driving and can make it do a loud click like rev click going uphill on normal incline in 3rd.

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27 Jun 2020 16:40
Jcummings2772
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1973 Yamaha DT-250 making terrible noise #8
I agree with others.
Could be a front sprocket slipping.
Clutch or clutch basket issues
If it idles and sounds ok through the rev range in neutral, I don’t see an issue with the crank/ cylinder/ piston.
But once you put a load on it on bumpy terrain, the sound appears.
It’ll be fun to see what it is when you find it

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27 Jun 2020 16:47
1971DT250
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1973 Yamaha DT-250 making terrible noise #9
Check the chain guide below the swing arm for grooves from the chain hitting it. Pull the sprocket cover off and see if the chain was rubbing on it. With that large rear sprocket you might have clearance issues.

The hours spent riding my Enduros is not deducted from my life span.
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27 Jun 2020 16:52
Jcummings2772
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1973 Yamaha DT-250 making terrible noise #10
As your sprocket wears, the teeth will develop a sharp point and the belly between the teeth will become deeper, hence making the teeth thinner. They will then start to chip and break allowing the chain to slip.
As for the clutch basket and plates, you gave to drain your oil, remove the Kickstarter and remove the clutch cover.
Then remove all of your clutch spring screws and pressure plate. Inspect the fingers on your basket for grooves. This will cause your plates to stick and sometimes pop when under load.
Also if the fingers are worn and a lot wider than the plates, that will cause them to pop too.
There are many good you tube videos that walk through clutch disassembly and repair if your not familiar with it.

*****to drain your engine oil, be sure to remove the plug closest to the kickstarter (right side) of the motor. The one on the left side is for your shifter detent plunger***

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