XR660R ate itself - why?


39 replies to this topic
  • weskc35k

Posted July 08, 2006 - 06:08 PM

#21

If the head bolts weren't tight,regardless of jetting it's game under dude we have a weiner.
That piston may have also been machined incorrectly as the numerals look upside down but the valve reliefs look to be the right way up'so can you look for an arrow on the top of the piston and tell us what way it do facing.
Aftermarket pistons don't you just love 'em.
All the conjecture in the world means nothing now fix it properly go back to a bored stock sleeve out to 628/630 so it is not an odd size so that it can be rebored in the future after your next incident if need be.

  • unclecameron

Posted July 08, 2006 - 09:36 PM

#22

The cam, camshaft lobes and valvetrain all look really good, I would guess if there was any oil starvation it would show up there. The arrow on the piston points to the exhaust side.

I'm still leaning toward getting it resleeved down to the 660 9:1 kit by thumper racing, mostly because I don't know what else was done, but the kit was put in 3/97 and it still ran prior to this and started first kick, so I'm guessing mostly everything else was okay and set up properly, I don't want to take a chance and screw that up somehow, I was told it ran really good, so I'm thinking maybe the motor was originally done right, and the guy just abused it by putting mid-grade pump gas in it?

The bike just slowly lost power on the freeway, then the guy pulled off and pushed it home, presumably pissed. It kicked over very smoothly and I didn't hear any noises, see any metal shavings in the oil or see anything when I attempted to look down the spark plug hole with a mirror and flashlight. It still had a little bit of comression left, but not much.

Is it normal to have to press out the wristpin?

Thanks,
Cameron
San Diego

  • weskc35k

Posted July 08, 2006 - 10:23 PM

#23

If the head bolts weren't tight you have the reason for it blowing itself to bits.
If you go to 660 you have no more overbores left.

  • XR6's_rule

Posted July 08, 2006 - 10:48 PM

#24

I recently had my XR6 apart (with 628 11:1 wiseco piston). It is common to have to press the piston pin out, mine was quite tight to get out. All XR's run quite hot and the heat and stress from the big piston cause tightness of the pin.

If the bike has been setup properly ie jetting etc and had run well for a period of time, I would say that pre-ignition caused your seizure. With my XR6 it simply wont run any lower octane fuel than 98. Otherwise it pings very badly to the point where it really shouldnt be ridden. I think this is where your bike went wrong.

In my opinion, if you're thinking of using the bike for prolonged highway riding, I would go for a lower compression piston, as getting the higher octane fuel can be hard in some places.

  • bigredxr

Posted July 09, 2006 - 04:24 AM

#25

I'm not doubting peoples years of experience with these engines and bikes, but I worked for Daimler Chrysler for 10 years as a service tech and have seen many engines 4cyl, v-8-s, etc that have come in with misfires caused by a dead coil on a cyl, bad plugs with no spark, or an dead injector that had no pulse width. Or for that matter cars that nromally run on 45psi fuel press that have a fuel pump failing that are at 18 psi. They'll barely pull themselves in the door. None of these problems on a 4 srtoke engine has ever caused a piston to melt down if the engine was in time and running the correct octane for the vehicle. Which still leads me to believe that there also had to be second cause to this gentleman's engine failure be it a piston to sidewall clearance issue, ring end gap and the rings were to tight or the guy that assembled the engine never checked oil press. Also a possibilty of a tooth off on the timing chain and was overly advavanced helping aid the detonation process. My point is check everything and look for the underlying cause. No offense to anybody else on this form; just trying to put a second view on the subject.

  • unclecameron

Posted July 09, 2006 - 07:14 AM

#26

The timing was correct, that was the first thing I checked, also the spark looked very good when kicking it over.

Thanks,
Cameron
San Diego

  • bigredxr

Posted July 09, 2006 - 07:25 AM

#27

Fair enough and good luck in your engine reassembly. Hopefully you'll be more skilled and successful than the guy u bought the bike from.

  • unclecameron

Posted July 10, 2006 - 09:21 AM

#28

Called Thumper Racing and they said this is common, in fact they stopped making the 100 octane pistons and only have a few replacements sitting around for this reason. He said guys would call pissed off and he would ask them if they ran pump gas and they'd swear they didn't but usually did. He said the loose head bolts wouldn't help any, but probably wouldn't cause it by itself.

So now they sell everyone the 660 Baja kit that runs 9:1 and he said you couldn't tell much difference between the two in horsepower, so I guess it's a much better deal, so here's the breakdown:

$75 labor to resleeve (8-10 day turnaround)
$89 bored sleeve
$165 piston, rings, wristpin
$40 head/base gasket (they're not stock Honda)

So it looks like I'll be out the door for around $400 with a carb cleaning, and have a decent 660, still not too bad, should be wailing through the desert here in a couple weeks :ride:

Thanks,
Cameron
San Diego

  • SniperTeamBravo

Posted July 12, 2006 - 01:33 PM

#29

My 2 cents, but I'd do something in a smaller displacement even a 630 or something like that with a compression of less than 10.5:1 because your reliability will be better, and the bike will run as good and live longer, especially in the heat. I remember when Al Bakers XRs only suggested a big fin head with anything over a 100mm bore. I think the 100mm is 630cc on the XR. Good luck, and keep me posted on the motor as Im interested in how reliable itll be with the 660cc kit in it!

  • XR6's_rule

Posted July 13, 2006 - 02:12 AM

#30

All the best with your rebuild. Seeing that you have the top-end down, if it hasnt been done already I would also get the valves reset/seals replaced as well as replacing the cam chain. I know it all sounds like too much money, but if you put in a new sleeve and piston and have leaky valves or valve stem seals or have a cam chain thats nearly out of adjustment, the bike may dissappoint you later. Wheras if you do all this stuff, you end up with a new top-end all over and have a bike that will run for years. Cheers,

Mark.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • bork

Posted July 16, 2006 - 06:05 AM

#31

All the best with your rebuild. Seeing that you have the top-end down, if it hasnt been done already I would also get the valves reset/seals replaced as well as replacing the cam chain. I know it all sounds like too much money, but if you put in a new sleeve and piston and have leaky valves or valve stem seals or have a cam chain thats nearly out of adjustment, the bike may dissappoint you later. Wheras if you do all this stuff, you end up with a new top-end all over and have a bike that will run for years. Cheers,

Mark.

I agree , Do it right the first time. unless you know 100% that the rest in question are good.

  • unclecameron

Posted August 05, 2006 - 05:28 PM

#32

Got it back together, and it fired right up, has illegal amount of power, and that's just breaking it in riding around the block a few times taking it easy.

Note: kicking it over with throttle at half will almost break your foot :thumbsup:

So now the setup looks like this:
XR660 Baja kit (dished piston custom made for Thumper Racing by Wiseco) with 9:1 compression, resleeved cylinder, base/head gasket. I'm runing 91 octane pump gas. Everything looked all shiny and went together fine, didn't even have bolts left over on the bench.

How long before I can wail on it, couple tanks, 500 miles, anyone have experience with what's best?

I'll let you know how it's running in 500 miles or so (couple weeks probably, I ride A LOT).

Thanks,
Cameron Camp
San Diego
San Diego Adventure Rider
www.dualsport-sd.com

  • rmhrc630

Posted August 05, 2006 - 05:56 PM

#33

Great news.

It's always good to hear thing work out when you have probs with the big XRs.

FWIW my pins terriblly on pump gas - running a high comp motors means I have to carry octane booster.

  • HawkGT

Posted August 05, 2006 - 06:35 PM

#34

Keep revs moderate at first but don't be afraid of full throttle. The high cylinder pressures are needed to ensure the best possible ring seat.

  • suharianu

Posted August 05, 2006 - 10:53 PM

#35

check your jetting so you dont blow your new engine again

  • unclecameron

Posted August 05, 2006 - 11:43 PM

#36

The jets are significantly larger than stock, which I would assume would be needed with high compression and drilled/K&N airbox/filter?

One small bit of stupidity:

I have extra o-rings in the kit, were one of them supposed to go on the idle adjust screw? Right now I have just the screw with that tiny spring under it, screwed all the way in, then backed 2 turns out, is this the right setup, I can't tell from the pictures I've found. It idles, but not very spectacularly, but I don't think I have an air leak. It runs really good off idle, I was just thinking it would take a little time to break in and idle right?

Thanks,
Cameron Camp
San Diego
San Diego Adventure Riders
www.dualsport-sd.com

  • HawkGT

Posted August 06, 2006 - 12:43 AM

#37

The jets are significantly larger than stock, which I would assume would be needed with high compression and drilled/K&N airbox/filter?

One small bit of stupidity:

I have extra o-rings in the kit, were one of them supposed to go on the idle adjust screw? Right now I have just the screw with that tiny spring under it, screwed all the way in, then backed 2 turns out, is this the right setup, I can't tell from the pictures I've found. It idles, but not very spectacularly, but I don't think I have an air leak. It runs really good off idle, I was just thinking it would take a little time to break in and idle right?

Thanks,
Cameron Camp
San Diego
San Diego Adventure Riders
www.dualsport-sd.com


The fuel screw should have a spring, then a washer, then an o-ring.

If you haven't confirmed the jetting since the rebuild then that should be on the top of your short list. What is the current jetting? Others with 660s might be able to give you guidence on a baseline from which you can work out the proper jetting for your bike in your location. "...significantly larger than stock, which I would assume...", is asking for trouble. Know the actual jetting and don't make assumptions or you could be rebuilding it all over again...

  • unclecameron

Posted August 06, 2006 - 02:41 PM

#38

The main jet is 172, idle is 65. Thanks for the tip on the idle adjust screw, that helped it run better :thumbsup:

Thanks,
Cameron
San Diego

  • bork

Posted August 07, 2006 - 05:04 AM

#39

How many $$$ do you think it took to fix?

  • unclecameron

Posted August 07, 2006 - 05:48 PM

#40

I'm out the door for about $500 give or take a steak dinner for 2.

Thanks,
Cameron
San Diego





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