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

http://uploads.tapatalk-cdn.com/20160518/4a6f48b4c52d3087df574845e71175da.jpg

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:
231881

Spark plug:
231882

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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[yaegerb]

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:
231881

Spark plug:
231882

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

Concerning your piston picture:
The "wash" on that piston screams too low of octane. See the dark ring around the perimeter of the piston? That is a sign that your fuel is detonating on the squish and not on the crown. what you should see is dark swirls or wash coming from the transfers and culminating to a chocolate ring on the crown. Your low octane fuel was pre igniting on the perimeter (hottest part of the piston). That's the sound I thought I heard, that's why I asked if you were using race gas. Lesson learned and you are lucky you didn't grenade that 310.

Concerning your spark plug picture:
That color is typical of race fuel (maybe a little darker). However, since you weren't running race fuel that grey is a sign of uber hot. Glad you caught this in time.

I recommend you run VP c-12 or Sunoco 110. Both are quality race fuels. Don't gamble with the race gas at the filling station unless you know 100% it fresh and clean. Typically that gas sits for long periods of time due to the high cost. Over time water develops in the tank and that's the right way for more problems.

[DohcBikes]

Also heard preignition. That's what steered me towards timing. Didn't know it wasn't adjustable.

[cobradude]

Thanks to all for your input! It was the comments about the timing that got me to thinking about it & the question about race gas that made me realize what I had done

Plan for now is that since I don't have easy access or extra funds for race gas, I will dig the pump gas dome out & run it. Plus it's in better shape with no gouges in it

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[oscarmayer]

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?

yea, I was thinking of something else, your right the stocker is not adjustable. sorry forgot about that.
===================

pull the cylinder and check the piston, if you ran the wrong fuel I am concerned over ring and cylinder damage.

[yaegerb]

Thanks to all for your input! It was the comments about the timing that got me to thinking about it & the question about race gas that made me realize what I had done

Plan for now is that since I don't have easy access or extra funds for race gas, I will dig the pump gas dome out & run it. Plus it's in better shape with no gouges in it

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I would highly advise you check compression. Don't just strap a "pump gas" head on and assume its OK. anything over 200 PSI I would encourage using race gas.

A UCCR and squish would be an even better check, but more labor intensive.

[Queef Chief]

as others mentioned, those sharp nicks in the dome can cause pre-ignition. couple that with with low octane in a race dome and it multiplies. keep us posted

[cobradude]

Sorry for the wait, got busy for a few days.

Here is a compression check, race gas dome:
http://uploads.tapatalk-cdn.com/20160521/ffae65e8840db42f7b6d4a0047dc3162.jpg

Pump gas dome:
http://uploads.tapatalk-cdn.com/20160521/52c117aec3cc795b74c9dbeb875d10c9.jpg

Both were done on a cold motor.

It runs much better up top with the pump dome, lost a bit of pep on the bottom.

Here's a new plug from today, with about 10 mins of run time on it, not a true plug chop yet, just getting more of a feel for how it's running now
http://uploads.tapatalk-cdn.com/20160521/0fa1b09b12478862a57e542149099959.jpg

On a side note, does anyone have a good source on the flanged acorn nuts used to hold the head on? I am in need of a new set.

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[loganm]

You can get them at autozone or oreilleys. Spent all day looking around for head studs since fastenal and Napa were closed. NAPA stocks them too , at least locally. Cannot find studs long enough at any auto parts store.

[yaegerb]

Glad you figured it out. That plug should be a little darker but looks ok.

Here's a good kit for your head nuts.

http://m.ebay.com/itm/HONDA-TRX250R-FOURTRAX-ATC-250R-ENGINE-BOLT-KIT-TOP-END-Cylinder-Head-Intake-/151864759769?hash=item235bd855d9:g:dfYAAOSwl9BWL-Pg

[cobradude]

Glad you figured it out. That plug should be a little darker but looks ok.

Here's a good kit for your head nuts.

http://m.ebay.com/itm/HONDA-TRX250R-FOURTRAX-ATC-250R-ENGINE-BOLT-KIT-TOP-END-Cylinder-Head-Intake-/151864759769?hash=item235bd855d9:g:dfYAAOSwl9BWL-Pg
Thanks for the eBay link, had my eye on that one myself.

Need a bit of help with the carb. Have the idle adjustment run all the way in, but idle is still a bit lower than I want it to be. Does that mean I need to make a change to the pilot jet? It currently has a 55 pilot & a 180 main in it

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[loganm]

Idle adjustment as in idle screw or air screw?

[RIDE-RED 250r]

How many turns out on your airscrew??

What carb? If it's a PWK, in my experience they seem to idle an R pretty slow and I end up having the idle speed screw all most all the way in. That is the case on my ESR 350 engine as well as my OEM cylinder on my second R.

I have heard of quite a few others experiencing this same issue. I think BDT Motorsports offers a longer idle speed screw for this little issue.

Having said that, a 55 pilot seems pretty fat for a 310. I'd have to look at the note in my jet kit, but I'm pretty sure my 350 is idling and running well on low end with a 50. I remember running a 52 in it during break-in and it was a bit blubbery down low and actually flood fouled a plug on me a couple times running slower woods trails.

Yeah, I write down my jetting on an index card and leave it right in my jet kit. I figured out a long time ago that no matter how simple it may seem to remember what jetting I'm running, I would always forget so I started recording it so I would know for future reference.

[cobradude]

Forgot to say, it's a pwk. & the air screw is out 2 turns. It is a bit blubbery on bottom, & doesn't pull a high gear well at all. Didn't know that about the idle screw being a bit short

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[RIDE-RED 250r]

Well, 2 turns out on the airscrew and still blubbery down low is a pretty good indicator that you need to go smaller with the pilot jet. I would bet yours settles in on a #48, but don't jump from a #55 all the way down to a #48. Take it down a step at a time till it's running and idling better with the airscrew between 1 and 1.5 turns out.

You say it doesn't pull a high gear well.. Do you mean high RPM?? Or just that when the RPM's are somewhat low in a higher gear it doesn't pull well. 180 main is right in there where I see alot of other guys running their 310 mills, maybe still a little on the rich side, but not outlandish.. If it cleans up with higher RPM you should be good. You might just be loading up your pipe with unburned fuel that accumulates when running as rich as you are down low... That's what my 350 was doing when I was running the 55 and 52 pilots.

[yaegerb]

Thanks for the eBay link, had my eye on that one myself.

Need a bit of help with the carb. Have the idle adjustment run all the way in, but idle is still a bit lower than I want it to be. Does that mean I need to make a change to the pilot jet? It currently has a 55 pilot & a 180 main in it

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If you are running an airbox with lid, go with 50 pilot and 170 main, needle on 4th clip from top.

And then put a fresh plug in and see what it's telling you.