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Old Yesterday, 08:20 AM   #1
therivermonster OP
Gnarly Adventurer
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Joined: Sep 2010
Location: Tacoma, WA
Oddometer: 329
DR650 Top End Rebuild

Life has been great with my trusty DR650. The bike has never let me down, and has taken me everywhere I have wanted to go. They are great bikes!

Then, the other day on the way home from work riding south bound on I5 from Seattle, I slowed for traffic ahead of me when WAM! A full size pickup truck rear ended me, and I found myself taking a nice pavement nap right in the middle of the freeway. Luckily the bike came through OK, but does need some minor repair. I'm doing my best to heal up with compression fractures to my lumbar spine.

I decided it was time to put some work into the bike getting it back into running order. The accident did a fair bit of damage to the exhaust and right side Wolfman racks, but one thing I wanted to resolve was a cold starting issue that has been plaguing the DR for about a year now.

A couple of months ago I installed a Mikuni TM 40 from Procycle which is a nice piece of hardware, but this didn't resolve my cold start issues which I was hopping it would. This last weekend I decided it was time to resolve this issue for good, so I broke out the tools and did a compression test that showed 65 PSI at WFO. The manual says that the cylinder should show 120 PSI for the compression test, so 65 wasn't good news. Next I brought the engine to TDC on the compression stroke so I could do a leak down test. As soon as I started to pump air into the cylinder I could hear it leaking out of the exhaust. When I walked to the back of the bike I could easily feel the air coming out of the tail pipe. The leak down gauge showed pressure way low on the left side of the gauge, but I don't remember the exact number. This was a clear sign that there was probably an issue with the exhaust valves so I pulled the head. This is what I found...

Odviously some valve work is in order, but the cylinder walls look OK I think. Do they look OK?

Anyhow, this is how the bike sits now.

I am currently in the process of trying to figure out how best to move forward. A friend of mine has used Action Cycle here in Tacoma in the past to have top end work done on his KLR, so I'll give him them a call today. I know that the bad valve will have to be replaced and probably that valve seat, but I'm not sure about the rest of the valves or the cylinder.

As I work through this rebuild, I will post updates here. If any of you experts have advice or tips on how best I should move forward with the repairs, or other things I should look into repairing or replacing I would love to hear about it.

One quick question to kick off the rebuild: What is the best way to clean the built up carbon from the head and top of the piston?

More to come soon...
“Behold, I am sending you out as sheep in the midst of wolves, so be wise as serpents and innocent as doves."

My Virgin ADV Trip
, Rocks Flyin', Me Cryin', and God Looking On - A WABDR Adventure, Fun With Carbon Fiber

therivermonster screwed with this post Yesterday at 11:08 AM
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Old Yesterday, 10:08 AM   #2
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Joined: Aug 2013
Location: Halfway to hell (WI.)
Oddometer: 885
How many miles on it and what year ?

I would have all the valves re-cut for new sealing surfaces as long as one is being done. I'd also get both exhaust valves new from Kibblewhite so both are done good.The intakes can be checked and reground with new surfaces. Have the bore mic'ed for roundness and any taper to be within spec. If good a quick hone for deglazing and fresh hatch'es for a new set of rings.

I don't know what year your bike is but before '03 they had bad base gaskets that should be replaced with the new metal version.

Glad you didn't get banged up too bad, I hate those cages that tailgate bikes which I bet is the case here.
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Yamaha XT600 x 3, ..Yamaha XT600E/600N,..Yamaha XT660(E) hybrid,....Honda XL600 ,... KTM 525XC , Suzuki '01 DR650 & '07 LTR450,
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Old Yesterday, 11:33 AM   #3
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Joined: Dec 2009
Location: North Carolina Y'all
Oddometer: 2,928
I posted over in the DR thread but saw you move it....I will put this here in case you don't see it over there...

Don't worry about the head if you are taking it to a machine shop- they will want to be the ones to clean it. Otherwise you might be making more work for them. As for the cylinder I would clean the gasket area and leave the piston alone if you don't plan on doing any machining with it. You will probably do more damage disturbing the carbon and getting it between rings than any good.

A good machine shop will be able to check the other valves and re surface them if they are within specs. Don't know what the cost of new valves is but I always recommend that. It looks to me in that pic the seat might also have a crack-hard to say. Even if it didn't I would replace it do to the excessive heat that has gone by it. It has had a hard life and may have shrunk up losing some of it's press fit. May fall out at a later date.

You may already know what caused that but I will give some ideas for those interested: Not enough valve to rocker clearance is one. It causes the hot combustion gases (normally valves are closed during the hottest part of combustion) to pass by the valve acting like a cutting torch. Initially it causes cracking then starts to burn away material. This would be my guess what happened here since the other exhaust valve looks fine.

The other two things that cause exhaust valve to burn up is lean mixture and retarded ignition timing(and by retarded I mean later than optimum- as little as 10 degrees retarded causes exhaust temps to sky rocket). This causes higher than normal exhaust gas temperatures which the valve is not designed to take. Leads to cracking then failure of the valves. I would expect to see issues with both exhaust valves if either of these were the case.

Tuliped intake valves can be an indication of retarded timing as well because intake valves are not made to take the excessive heat- get soft- then start to pull into the head.
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Old Yesterday, 12:11 PM   #4
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Joined: Dec 2008
Location: Littleton, CO
Oddometer: 2,468
Find out why it burnt the valve. For some reason it's too lean, or more likely the valve adjustment is too tight.. If it is still too lean or still adjusted too tight when you put it back together it will burn the new valve just the same way.

My first guess would be valve clearances, or the new carburetor was not jetted correctly.
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Old Yesterday, 12:28 PM   #5
therivermonster OP
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Joined: Sep 2010
Location: Tacoma, WA
Oddometer: 329
Thanks, JJXTRider!

The DR is an 05 has almost 46K miles on it so far. It wouldn't have the paper base gasket, however I think that I'll still pull the cylinder and have it specked and honed.

After a quick search, I found Kibblewhite valves for the smaller DRs and the DR800, but not for the 650. I know Pro Cycle sells the set of four oversize valves, but those aren't a direct replacement, right?

Should I source OEM replacement rings from a dealer, or is there a better source? Also, would the rings need to be filed to fit most likely?

I would assume that the piston, wrist pin and related hardware are OK to reuse?

It looks like I should be able to get the rest of the seals, o-rings, etc from Pro Cycle.

I also plan to inspect the transmission gears as much as possible while the piston is out. My last oil change (which was LONG overdue) showed a fair ammount of metal filings on the magnetic drain plug.

Thanks again!

“Behold, I am sending you out as sheep in the midst of wolves, so be wise as serpents and innocent as doves."

My Virgin ADV Trip
, Rocks Flyin', Me Cryin', and God Looking On - A WABDR Adventure, Fun With Carbon Fiber
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Old Yesterday, 04:08 PM   #6
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Joined: Nov 2010
Location: Snowy Mountains Oz
Oddometer: 3,596
That's a LOT of steel on the plug

Have a real good look at the gear teeth, the case hardening does seem to go first and then it gets worse.
shed time IS quality time
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