Warped/bent exhaust valve?
-
Enjoy XS650.com? Consider making a donation to help support the site.
XS650.com receives a small share of sales from some links on this page, but direct donations have a much greater impact on keeping this site going.
She should of hid the van keys
- Thread starter gggGary
- Start date
Lotsa carbon on the exhaust valve face.
How does the exhaust guide feel? Is the valve stem seal shot? The stuttering on the exhaust seat means something, just can't remember where I saw it before and what the problem was. Gaps on oil control rings?
Thnx. will get that valve in a collet and spin it tomorrow.
Will change seals for sure, nothing obvious on loose valve or bad seal.
Haven't checked ring gaps.
Will change seals for sure, nothing obvious on loose valve or bad seal.
Haven't checked ring gaps.
Last edited:
That’s a crazy looking piston / head design. That dished piston instead of the usual domed one, and a flat head? I read an article a couple years ago about a guy trying to up the performance on one of these ( Huron ? ) motors, he milled the heads to up the compression. In the end he expended a lot of effort and didn’t add much to the performance.
So what do you figure was the chain of events? Carbon build up in the exhaust valve seat, then loss of compression , leading to all that built up gunk? Then unburned fuel passing to the catalytic converters turned the muffler blue?
So what do you figure was the chain of events? Carbon build up in the exhaust valve seat, then loss of compression , leading to all that built up gunk? Then unburned fuel passing to the catalytic converters turned the muffler blue?
All the oil is what's buggin' me. Figure that's what was on the plug.
Yeah interesting design. I suspect cheap to build, a major consideration. 750cc making 50 HP, valves are pretty small, but not much room on a flat head.
Speaking of flat the machining not the finest I've seen, might be enough of a wave from the milling to pass oil but was no evidence the head gasket was compromised. It has a Crankcase vent goes to the intake mebbie an oil overfill was sending oil into the cylinders fast enough that it carboned up the exhaust seat and lowered compression? lots of oil being burned in the cat caused the bluing? specially once the exhaust valve was leaking? Note the carbon build up "ridge" on the piston and heavy smear on head. Would only take one chunk of that on valve seat to "cascade" I checked oil soon after I got it here level was normal. PO had changed oil and filter in 2017 prolly less than 1,000 miles ago. Haven't stuck the borescope in good side to see if it has a lot of carbon build up. (tomorrow.) The other cat was running pretty hot also.
The thing is I capped the ports and let the crank vents hang open for ride yesterday. Still a lot of oil on that plug.
Yeah interesting design. I suspect cheap to build, a major consideration. 750cc making 50 HP, valves are pretty small, but not much room on a flat head.
Speaking of flat the machining not the finest I've seen, might be enough of a wave from the milling to pass oil but was no evidence the head gasket was compromised. It has a Crankcase vent goes to the intake mebbie an oil overfill was sending oil into the cylinders fast enough that it carboned up the exhaust seat and lowered compression? lots of oil being burned in the cat caused the bluing? specially once the exhaust valve was leaking? Note the carbon build up "ridge" on the piston and heavy smear on head. Would only take one chunk of that on valve seat to "cascade" I checked oil soon after I got it here level was normal. PO had changed oil and filter in 2017 prolly less than 1,000 miles ago. Haven't stuck the borescope in good side to see if it has a lot of carbon build up. (tomorrow.) The other cat was running pretty hot also.
The thing is I capped the ports and let the crank vents hang open for ride yesterday. Still a lot of oil on that plug.
I’m enjoying following along as you figure this out. I always learn something new. It’s like figuring out a puzzle.
Bike was pretty low miles for such drama.
Bike was pretty low miles for such drama.
So would a valve getting slammed closed on a chunk of carbon throw it enough off center to cause it to act like an oil pump?
Don't ask me to explain the physics of it ('cause I can't), but it's been my experience that a (relatively) clean piston points to the oil ring.
Why? It would be a shame to have an engine this far apart and not re-ring the pistons...
JRP01
XS650 Enthusiast
tarp
JRP01
XS650 Enthusiast
At least i changed the clutch cable. ha ha.Shoei but not that old prolly going on 10 though.
So with JRP1 'round the radian project was cooling it's heels. But got back at yesterday and today.
New clutch cable installed. Both slipping clutch and hard to find neutral "cured".
Set the valves, shim over bucket, will need to order a couple shims to finish the job, about half were fine, the others needed one size thicker shim. Not a bad job on this motor. Thanks to Mr. Bultaco for some shims and the Yamaha tool! Still need to set the cam chain.
New spark plugs, it had one range too hot plugs in it. Compression cold 158. 151, 147, 155, good for a cold engine with not many recent miles.
That darned mailman, he jinxed the carbs. So off they came, and they got the full monte yesterday.
Lots of fine sediment in all the float bowls,
View attachment 146443
One carb was not bolted to the rack, one float valve was missing it's rubber tip.
Hint the Radians use an o-ring to seal the float valve body to the carb body just like BS34s but they must have changed the rubber formula. All 4 were glued into place, this was a case on a Radian I had a few years ago also. So I made a float valve body gripper and twisted firmly til the body released. Turns out I literally shredded the o-rings to get them loose!
View attachment 146442
Also shows why you just have to remove them, the screens above the valve were loaded. Rest of the carbs really were pretty decent, no badly plugged jets or orifices. Kind of snug getting them in and out but got 'em all in place, buttoned up, put on a temp fuel tank and dag nab it they started leaking! Tried fuel on and off three times, no joy, started to unhook to remove and wait a minute! I had installed an aftermarket inline clear square fuel filter and it was split at a seam, leaking gas, that was it! the filter was bad, my carbs were fine, Woo Hoo. Drained fuel tank, dried, shook a chain in it and blew out the dust. Got a petcock rebuild kit, a few parts from it fit (grr) and worked but was able to get it together and working as it should, automatic fuel again.Added a quarter turn valve to the fuel line "just in case"
View attachment 146444
These little Briggs and Stratton valves aren't cheap, about $7.50 at Farm and Fleet but they WORK! I have one on my test tank, a couple years now. Tried a couple cheap Chinese quarter turn valves, made of metal but they were all junk, quickly started leaking big time.
Bike started, ran, idled great.
Moving on, pulled the front wheel, replaced tire with new Shinko, balanced, and installed. These use a 16" front and rear, the front 110/90/16 is a pretty rare size. Front pads were about to metal on one side, so pulled, cleaned the calipers and replaced the pads. Since I had the pistons fully retracted I sucked all the brake fluid out of the reservoir and refilled, pulled brake lever off and cleaned, greased the pivot. Pads pumped out to the rotors easily, full hard lever. Prolly do a full brake strip next winter. Just got back from a test ride, all is good. Low RPM power much improved. Very smooth and loves to rev, not that Allison will do that! Still need to do chain and front sprocket, rear tire. But that can wait a few days, Allison can ride it to work.
JRP01
XS650 Enthusiast
I use it all the time to monitor my Ford E350 Motorhome. Also reset OBD11 monitor on Tundra. Great tool.
JRP01
XS650 Enthusiast
tive; however, some are an
hard to tell from pics but that cylinder looks awfully shiny. Rings may not be sealing perfectly. I suggest honing with stones and a good wash then new rings. Obviously a ton of oil flowing through there. It may have coked on the exhaust valve. Definitely need a valve job. You can probably clean up the seats with a cutter. If the valves run straight in lathe can clean cut but they are almost certainly hard faced so better to replace them in my opinion.
Thanks JRP1 knew you'd come through, Headed down to Herman's motor clinic for him to take a looky see also.
JRP01
XS650 Enthusiast
Gee must be n
Must be nice to have an actual machine shop within a days drive ha ha.
Gary - I looked down into the heads with the valves out (see Jim's marked-up photos in Post #101 above) - do I see damaged valve guides?
The ends of the guides that are visible deep down in the intake and exhaust ports look sort of dinged-up to me...
I certainly agree about new rings, hone and new valves. Whatever has been going on in there has sure made an awful mess out of that spark plug. I don't think I have ever seen a Japanese engine in such dire shape with such low miles on it. Its almost like someone put diesel fuel in it by mistake....
....hmmmmm.
Pete
The ends of the guides that are visible deep down in the intake and exhaust ports look sort of dinged-up to me...
I certainly agree about new rings, hone and new valves. Whatever has been going on in there has sure made an awful mess out of that spark plug. I don't think I have ever seen a Japanese engine in such dire shape with such low miles on it. Its almost like someone put diesel fuel in it by mistake....
....hmmmmm.
Pete
Last edited:
Mr. engine shop is going to give it a spit and polish; quick look valves, guides are good. Guess you can kinda tell a valve is straight when it makes a nice thwick sound when you slap it closed.
Wasn't pay'n attention, it's a "nikasil" coated cylinder. That's a bottomless pit of searching https://thumpertalk.com/forums/topi...obs-the-big-question-nikasil-and-iron-sleeve/ So might NOT hone...
Omission; I had retorqed head studs to spec, they all needed it. Probably shoulda just run it another 100 miles, see what happened.
Will retorque other side in a bit.
Wasn't pay'n attention, it's a "nikasil" coated cylinder. That's a bottomless pit of searching https://thumpertalk.com/forums/topi...obs-the-big-question-nikasil-and-iron-sleeve/ So might NOT hone...
Omission; I had retorqed head studs to spec, they all needed it. Probably shoulda just run it another 100 miles, see what happened.
Will retorque other side in a bit.
Last edited:
Mr. Machine shop called today; come pick up the parts.
He didn't come right out and say it but I think the factory exhaust seat was not "real concentric" with guide.
So seat recut, valves lapped. Bore, checked, round, light ball hone. Rings, valve seals, gaskets, on the way. Maybe back on the road for the weekend?
He didn't come right out and say it but I think the factory exhaust seat was not "real concentric" with guide.
So seat recut, valves lapped. Bore, checked, round, light ball hone. Rings, valve seals, gaskets, on the way. Maybe back on the road for the weekend?
Last edited:
Looks good! You just did the one jug right? Since the other had such good compression?
