Won’t Rev out

[Farmingstock]

I have a 1993 Yamaha DT50, bought as a none runner basket case, put a top end on it and now it starts every time, absolutely fine.

If I go through the gears quarter throttle it is fine, however if I open the throttle up, it will almost rev fully but from then onwards it completely bogs and splutters.

If I put the choke on whilst it’s bogging it will momentarily pick up but only for a second.

I have tried cleaning the carb several times and it hasn’t made a difference, tried a new plug with no change, the reeds are clear.

I did a compression test and it’s only 60psi, I’ve tried to find the spec but not found anything at all?

I’ve ordered a larger jet but not holding my breath! Any other things to check??

The bike has an aftermarket cone air filter and I think it’s an aftermarket exhaust also.

[Nobby the Bastard]

60 psi is fuck all. If you are lucky just the rings but you are realistically looking at a rebore and piston kit.

Fucking with jets won't fix the lack of compression.

Fix that and then rejet to suit whatever abuse the intake and exhaust have been subjected to but remember that yamaha spent millions developing it so standard exhaust, jetting and intake will always make it more usable.than 16 year old Kevin and his deranged ideas about tuning can.
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[Farmingstock]

I’ve just replaced the barrel and piston, maybe the rings haven’t bedded in yet? Done less than a mile since rebuild, should I be complaining to the parts suppliers?

Exhaust and filter were on the bike when I got it, along with the blown top end.

[Nobby the Bastard]

Did you check that the barrel and piston/rings were matched? If I remember correctly the piston sizes went up by 0.25mm up to 1mm oversize.

If you have the wrong rings or pistons for the barrel diameter it'll be crap.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[Farmingstock]

It was bought as a kit barrel, piston, rings (upper, lower and crush), pin and gasket set from Yambits, bought og little end from Yamaha.

Big end had a very small amount of side to side but no up and down play.

The bike starts perfectly, I have googled “DT50 compression test” and the only ones I can find say 50-60psi, I genuinely thought it would be more.

The bike does have spurts of running good but only lasts for seconds, tried taking the main jet out to check it with more fuel but probably to much fuel, will try moving the clip but can’t see it doing much.

[Easy-X]

60 is way too low, probably half what it should be.

Unless specifically mentioned in a kit you'd still need to check the ring gaps. I'd pop the head off and take a peek as incorrectly gapped rings might expand and damage the cylinder.
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Nobby the Bastard]

Is it a 2t? I thought they all were but I'm confused by your 'crush ring'.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[Farmingstock]

Yeah 2 stroke, the kit cam with a crinkled ring that is placed under the actual ring, been on a few forums and they all seam to be saying dt50’s have unusually low compression.

[Nobby the Bastard]

That sounds like a oil control ring from a 4 stroke. I've never heard of a 2t having an ring like that.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[Nobby the Bastard]

According to this a 96 dt has a standard pair of rings and no crinkled one.

https://www.fowlersparts.co.uk/parts/3990750/dt50r-4ct6-1996-999-a/crankshaft-piston
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[Nobby the Bastard]

Anyway. Have you done a plug chop?
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[Easy-X]

[Farmingstock]

It’s the earlier air cooled model, don’t know if that makes a difference.

Done a plug chop what do you guys think?

[Farmingstock]

This is the kit and the exhaust in the pic is exactly the same as the one it has on.

[Nobby the Bastard]

That is running really rich.

If that kit is exactly the same as the one you got, where's the crinkly ring?
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[Farmingstock]

The kit came with it, so I used it. Anyway did another plug chop with a brand new plug although it won’t Rev out so don’t know how much use it is? The bike seams to get really hot really quickly!

[Farmingstock]

This is what the bike does, full throttle!

[redeem ouzzer]

There is a lack to 2T knowledge on here. He's talking about an expander ring which goes under the bottom ring, very common. Supposed to help with excessive piston noise. Some people use them, other's don't (as they can break up and find their way out of the ring groove).

Have you measured the ring gap?
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Be a REAL MAN!

[Farmingstock]

Think I’ve cured it, looks like there was some air leaks, adjusted the float bowl slightly, it revs out in 1st,2nd,3rd doesn’t do anything in 4th,5th but that maybe just coz it’s slow.

This is the plug now