DR350 Thread

[RuggedExposure]

The bowl:




The tip still looks new:


Inside the float valve is clean and has a new o-ring (thanks to the badass Mr. Bender)




I didn't take apart the slide assembly just to show pics of the needle, but the needle is in the 2nd position from the top and everything is assembled correctly. Also, there is little to no play in the slide (moving it from airbox to engine direction) and no side to side play:

[RuggedExposure]

Here is the choke/enrichener with the o-ring in place:


and the port it goes into is clean:




This carb is seriously clean enough to drink out of. Every nook, cranny, jet, emulsion tube, and piece that is removable has been acid washed, scrubbed and cleaned. Nothing has been changed from when it was running great.




I got the jug off:


Like most of you know, I'm no expert. But the inside looks really smooth and almost no scoring from the rings except for these little marks:

They are criss crossed... obviously the rings didn't do this???

and the piston:

[2bold2getold]

Originally Posted by RuggedExposure

Like most of you know, I'm no expert. But the inside looks really smooth and almost no scoring from the rings except for these little marks:

They are criss crossed... obviously the rings didn't do this???

The cross hatch on the cylinder wall is caused by the finish hone rotating and moving up and down slowly in the final step of honing the cyl to the correct size. It's supposed to produce a finish to hold the correct amount of oil and help seat (wear in) the rings. I've seen worse looking bores and the rings don't look stuck or worn down to nothing. Still wouldn't use em back. The best bang for the buck is to replace every thing you can with new parts, up to a point. Other wise you've got your same old motor back, and all that time, work and money for nothing. The piston should have an arrow on the top that points forward (exhaust side). On most pistons the wrist pin is off set to on side, either front or back depending crank shaft direction of rotation. to help with piston slap noise.

[PHILinFRANCE]

Originally Posted by 2bold2getold

Hi Phil. did you check the rubber o-ring that holds the seat in the carb body. If it's bad, gas will flow around the seat into the float bowl. The 1/4 inch pin is called the "needle" and the other part of the float valve is called the "seat" (needle rests on the seat to stop gas flow). Or float sunk (partially full of gas).

Cheers mate
The o-ring looks ok but will give it another looking at and i'll check the floats , but all 3 to have a hole seems unlikely

Phil

[tntmo]

That is called cross-hatching. It's good if it's still there, means there is very little wear in the cylinder. That looks great. A couple of scratches in the lower left of the picture...can you feel those with your fingernail?

Originally Posted by RuggedExposure

Like most of you know, I'm no expert. But the inside looks really smooth and almost no scoring from the rings except for these little marks:

[tntmo]

Oh yeah, I also wanted to let you know that I never use a ring compressor on the DR piston. Just squeeze the rings together by hand as the piston goes into the cylinder. It's slightly tapered on the bottom and goes together easy.

[2bold2getold]

Originally Posted by PHILinFRANCE

Cheers mate
The o-ring looks ok but will give it another looking at and i'll check the floats , but all 3 to have a hole seems unlikely

Phil

That fuel's got only one way in there. It's got to be going around the seat (o-ring) or past the needle (needle/seat interface or not enough float pressure) or too much fuel pressure from stopped up tank vent???

[Vankaye]

Hang in there Man! We've all had bikes that tried to out wit us. But you're doing great!

Sorry, i have nothing technical to offer you at this point. You're in over my head

Oh, how do the ring retention pins look inside the ring grooves? If the rings are able to jump
the pins that could cause enough blow-by to kill the compression.

[Wadester]

Originally Posted by RuggedExposure

I got the jug off:


Like most of you know, I'm no expert. But the inside looks really smooth and almost no scoring from the rings except for these little marks:

They are criss crossed... obviously the rings didn't do this???

Yeah, that's from the last hone job - on the other hand, those marks look way fresh! Like PO did a ring job and it didn't take. I have done cheapie ring jobs on cars - just ridge ream/hone/new rings and keep on. Usually works fairly well. But also, with hard rings (cr-mo) sometimes they don't seat properly - tho this usually means excess blow-by (crankcase gets combustion gas). I have had old rings unseat and lose all compression - perhaps this was a way-cheapie job, with old rings but a new hone job? You'd need to measure the bore to tell - maybe take it with you and let a shop measure it. If it is past a certain size, you'd need to bore it (check manual).

[mouthfulloflake]

I would put the piston and cylinder back together, verify your timing chain/cam relationship to the crank.

and look elsewhere for your issue.

[Greg Bender]

Originally Posted by Vankaye

Hang in there Man! We've all had bikes that tried to out wit us. But you're doing great

I had a Moto Guzzi V700 that gave me fits after getting warmed up and having no power. I checked everything over and over again (read = *many* hours). Come to find out two of the push rods were expanding (with heat) at an odd rate. No one had ever heard of that one before (particularly because the ends were tight and the tubes were not full of oil). Once I swapped the push rods, all was right with the world. But I chased my tail a long time getting to that point.

Regards,

Gregory Bender

[RuggedExposure]

Originally Posted by tntmo

That is called cross-hatching. It's good if it's still there, means there is very little wear in the cylinder. That looks great. A couple of scratches in the lower left of the picture...can you feel those with your fingernail?

No, those are very fine and cannot be felt with the fingernail.

Originally Posted by Vankaye

Hang in there Man! We've all had bikes that tried to out wit us. But you're doing great!

Sorry, i have nothing technical to offer you at this point. You're in over my head

Oh, how do the ring retention pins look inside the ring grooves? If the rings are able to jump
the pins that could cause enough blow-by to kill the compression.

I did not know there are any pins in the ring grooves, I'll have to look closer at the piston tomorrow. its almost my bed time.

Originally Posted by Wadester

Yeah, that's from the last hone job - on the other hand, those marks look way fresh! Like PO did a ring job and it didn't take. I have done cheapie ring jobs on cars - just ridge ream/hone/new rings and keep on. Usually works fairly well. But also, with hard rings (cr-mo) sometimes they don't seat properly - tho this usually means excess blow-by (crankcase gets combustion gas). I have had old rings unseat and lose all compression - perhaps this was a way-cheapie job, with old rings but a new hone job? You'd need to measure the bore to tell - maybe take it with you and let a shop measure it. If it is past a certain size, you'd need to bore it (check manual).

I doubt the PO did any sort of piston work to this bike. According to him it probably didn't even have 2k miles on it and I believe him. The bike never left his pecan farm and everything else on it is pretty much new. Is it possible that my auto-decomp in the cam is what took a shit?

Remember that this bike ran like a raped ape for 2-3k miles. Then on one 2hr trip it started having problems and has been getting worse and worse. It barely had compression when I took it apart (whereas a few weeks ago when it first started showing signs of problems it would still start and idle fine).

Maybe the auto-decomp is the culprit for everything???

[2bold2getold]

Some pistons have those little ring locating pins, Most don't. I doubt if the DR350 has em.

Here's some head/auto decomp info from DisTech's thread. Doesn't look like much to screw up, unless something got in there and jammed the mechanism.

http://www.advrider.com/forums/showt...=528784&page=6

[2bold2getold]

Originally Posted by mwilliamshs

I picked up a 99 dr350se and a 93 dr250se this weekend. Both need batteries. The 350 sounds draggy turning over like maybe a starter issue but I won't know for sure till I try it with a fresh battery. It does seem pretty noisy in the engine area to me, much noisier than the 250. Thinking the valves are at least out of adjustment so I've moved adjusting them to the top of the maintenance list. Anybody replaced a cam chain in one of these? Anything to replace besides the chain? Gears, guides, etc? I'll check valves and cam chain tensioner before getting more serious about the chain job but I'm trying to get a game plan in mind since I only see the bikes 1 day a week at most right now and they're 120 miles away round trip. Also, what's stock sprocket sizes for this?? I've looked around but all I can find are recommended combo's for off road grunt, highway revving, etc. Nobody wants to discuss stock apparently. I've got several front sprockets for experimenting but curious about stock as a baseline. Anybody know what stock sprockets for the 93 250se would be? Anybody have any advice for sprocket combos to ride the TAT through AR, OK, NM and Eastern CO then ride back to AR @ ~ 55 mph on asphalt(not interstate)? Thanks!

Here's you some gearing info also from DisTech's thread. http://www.advrider.com/forums/showp...&postcount=120

[slartidbartfast]

On one of my XS650s dirt dauber wasps sealed off the air gap between the cylinders. Subsequent local overheating (maybe) led to overheating of the rings and the oil control ring lost its "spring". In my case the bike just started making huge clouds of smoke but if the compression ring lost its temper, you would lose compression.

If you've got it apart, touch up the honing (if you don't know the technique to get good cross-hatch, get someone who's done it before to help you) and replace the rings. It won't cost much and you will have eliminated one potential source of the problem.

Did you check the valve timing before you pulled the head off?