Opinion wanted please

[cobradude]

Please excuse the horrible video, in need of a bit of tuning help, I have a hearing loss, cannot hear these 2 strokes as I once could. Bike is a '86 250r, with a CT Racing 310cc top end, on the 73.5mm bore. "Race gas done" 38mm pwk carb, 180 main jet, 55 pilot. No airbox, k&n filter. DG expansion pipe with DG silencer, repacked with less than 30 mins ride time on it.

In the video I am rolling into the throttle, but shifting when I get into the powerband, the transition point is very violent (loss of traction, etc.)

My question is, by sound, does the bike sound healthy?

https://youtu.be/LMw2jkjObf8

[IMG][/IMG]

Picture of the dome, if it can help with anything

[DohcBikes]

Check your timing. That's all I got.

[cobradude]

Both, please elaborate. I'm kinda hung up here, not sure what step I should take next. I just wanted to know the WHY

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[loganm]

Check your timing. That's all I got.

Definitely sounds like timing to me.

[oscarmayer]

there are slots the igniter coil sits in and you can rotate it different directions to adjust when the pickup will sense it. also that head, it is in BAD shape. those gouges can cause improper firing as fuel droplets will stock and it will interrupt flow dynamics in the chambers. send the head off to get the camber machined correctly to be smooth like it should be.
it also looks like you have a similar issue that we had. it appears your getting coolant into the combustion chamber. this can be from bad O-ring gasket, head is not decked properly, cylinder is not decked properly, damage to head or cylinder resulting in improper sealing off of the water ports to the combustion chambers.
the outside color looks just like coolant being burned off.
w/o getting my hands on the head I could not confirm, but by the photos it looks like the head is not flat.

[cobradude]

there are slots the igniter coil sits in and you can rotate it different directions to adjust when the pickup will sense it. also that head, it is in BAD shape. those gouges can cause improper firing as fuel droplets will stock and it will interrupt flow dynamics in the chambers. send the head off to get the camber machined correctly to be smooth like it should be.
it also looks like you have a similar issue that we had. it appears your getting coolant into the combustion chamber. this can be from bad O-ring gasket, head is not decked properly, cylinder is not decked properly, damage to head or cylinder resulting in improper sealing off of the water ports to the combustion chambers.
the outside color looks just like coolant being burned off.
w/o getting my hands on the head I could not confirm, but by the photos it looks like the head is not flat.

Ok, the video posted is from yesterday. This past weekend I redid all gaskets & o-rings in the top end, that is also when the picture of the head was taken.

So, the coolant leaks have been addressed. (I think). The head was smoothed out before reassembly. I didn't realize the head was THAT bad.

Speaking of timing, is the reason it is suspect is because of the sound it is making at higher rpms?

[DohcBikes]

It's the extremely sudden hit that makes me suspect timing. Or an ignition issue of some sort. And yes, it can cause all kinds of funked up sounds If the ignition system is not properly functioning. There are multiple components that could be malfunctioning.

[yaegerb]

Something doesn't sound right.....

85-86 in stock form isn't adjustable from a timing perspective, unless you have an adjustable timing plate. Furthermore, if you had sheared the flywheel key you wouldn't be moving that well. Do you have an adjustable timing plate? If not, move on. Pilot size is irrelevant at this point because (going from the vid you posted) you are moving between needle and main.


1. What's your compression?
2. Are you actually using FRESH race gas?
3. Post a picture of your plug please (need to see strap/electrode and porcelain)
4. What clip is your needle on?

[JesseA420]

is this all stock ignition components?

what is the portwork?

the dg pipes in my experience are worse than stock pipes. first thing i would do is replace with stock or decent aftermarket pc.


sounds just like its breaking up on mid top to me. main seems big for that pipe and a 310?

[JacobMonster]

QUOTE=yaegerb;1414758]Something doesn't sound right.....
[/QUOTE]
Please forgive me if Im wrong or dont know what Im talking about, but to throw something out there, couldn't it be his reeds are clogged, worn out, or to much oil in the gas?
Reason being is my dad's 91 KX does the same thing when you haven't held it wide open on the first ride. After you do that for a few seconds, it clears out, rides normal and doesn't do it again until the next ride. We let the gas sit for long periods of time running 32:1 pump gas.

Thats atleast what I think causes the issue Or possibly in high RPMs hes squirting to much coolant into the head.

(Pardon if my 2 stroke knowledge is completley wrong


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[yaegerb]

Please forgive me if Im wrong or dont know what Im talking about, but to throw something out there, couldn't it be his reeds are clogged, worn out, or to much oil in the gas?
Reason being is my dad's 91 KX does the same thing when you haven't held it wide open on the first ride. After you do that for a few seconds, it clears out, rides normal and doesn't do it again until the next ride. We let the gas sit for long periods of time running 32:1 pump gas.

Thats atleast what I think causes the issue Or possibly in high RPMs hes squirting to much coolant into the head.

(Pardon if my 2 stroke knowledge is completley wrong


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Could be a potential issue, but I want to rule out carb and other issues first.

[DohcBikes]

Make sure the jet needle isn't floating around in there. As in, be sure the "w" clip is in place

[cobradude]

WARNING: EPIC BRAIN FART

When I got home from work today, some parts for my kdx had arrived in the mail. Got the petcock rebuilt, reached for the gas jug & noticed it felt a bit light. Then it dawned on me: I had filled the 250r with the kdx's gas (93 octane).

I don't currently have any race gas, (thought I did), but I do have a pump gas dome for the 310 cylinder.

Tore it down:


Spark plug:


Gonna take the pump dome & the head to work with me tomorrow & ask my machinist buddy to verify the flatness, & just go with it.

[RIDE-RED 250r]

Yep, running 93 octane in an engine designed for race fuel, (I'm guessing 108 or higher) isn't good practice!

Hopefully that was your issue. It does sound weird in the midrange...

[cobradude]

Yep, running 93 octane in an engine designed for race fuel, (I'm guessing 108 or higher) isn't good practice!

Hopefully that was your issue. It does sound weird in the midrange...

Hope so, I will report back when I get it back together

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