Intro - Valve/Engine life?

[Caseyjones955]

Good afternoon all,

I live in the Black Hills of SD but bought my machine new in 00 while living in Seattle area. I have the 00 ST model. I love this bike, only mods are a custom seat, K&N filter and Wolf exhaust can w/FI remap. I have ~55k trouble free mi on this machine.

I have a very slight steady stumble at idle, flat spot just off idle and overall drop in power, slight hiway speed vibration, very slight but still detectable. The onset of all these things were simultaneous. I tried to synch the throttle bodies but deduct that I cannot do it correctly with my Uni-Syn and need a manometer, I am adjusting the valves while I have it apart. Compression is within spec and at last valve adjustment a leakdown test was performed and passed.

How many miles can a reasonably ridden and meticulously maintained 955 go before needing a valve job or possibly more? bottom end life? I realize variables exist but looking for a ballpark idea. Wisdom and experience appriciated.

Tony

[Stiles]

IIRC 955s have gone in excess of 100,000 miles on the original engine without major work. Some of the 1050s have needed a cam chain before that mark but I don't know if it's been more than a rarity.

It's hard to say what your bike's issue might be without more info. There's a lot of minor things that can cause a slightly rough idle.

[vdlcinc]

I just sold my 01 RS with just over 105K miles (all mine)... never needed more than just maintenance (oil, tires, valve adjusts, etc...)

Then turned around and bought an 00 ST with just over 30K... looking forward to the next 70K miles...

[Shovelstrokeed]

Things that can cause what you are experiencing can vary from the simple (spark plugs or iginition coil(s)/wires) to the sublime, stretched cam chain causing erratic valve timing, to the mundane (minor deterioration of valve seating surfaces).

Other possibilities are worn throttle shaft bushings leading to slight vacuum leaks, deteriorated vacuum lines or throttle body boots, due to heat, injectors that are gummed up and not delivering proper spray/atomization, injector to throttle body seals again causing slight vacuum leaks.

You mentioned a leak down test and the fact that the motor passed but, what was the percentage of leak down? What is the warm cranking compression done with all plugs out and the throttles wide open? Is it even across all cylinders? How about coil resistance?

The bike is 9 years old now, when was the last time you checked all of the engine and frame grounds for corrosion?

As you can see, you have a bunch of diagnostics to do.

[Caseyjones955]

Thank you for all the good responses. I cant recall the % on leakdown, only that he commented that its still a tight engine but that one of the valves was snug, this was a few k mi ago. I will make sure valves are adj correctly, measure resistances along the coils per the book and fire it to check for vac leaks and get another good comp test, see if I can synch up the throttle bodies and see where that lands me.

Any simple way to check timing chain for stretch while I have the VC off the engine?

Thanks again, I would love to squeeze another 50K out of it before I need to start combing ebay for a balled up low milage 955.

Tony

[DaveM]

Hi and welcome to the Sprint forum Caseyjones955

I am not all that technical so I will give my big mouth shut on that stuff and let those more able do the talking.

I would like to ask you as we do with every new member could you please take time to read our forum stickies just to get an idea of how we do things here?

No you have not done anything wrong we just ask every one to do it

cheers
DaveM

[Shovelstrokeed]

I wouldn't get all bent out of shape on the timing chain issue. I did say it would be in the sublime category. No easy way to check them anyway. You have to slack off the tension and then measure across some number of pins that varies with the chain mfg.

A really easy way to check for vacuum leaks is to use an unlit, but running, propane torch. Move the torch over suspect areas and listen for change in RPM.

[Caseyjones955]

Again, thanks for all the useful responses. I believe I have found the problem, or at least a problem... simple stuff first, right?

I rechecked valves this morning and found the exhaust valves to all be within spec.

Intake valves, 3 of which are so tight that I can't get my 0.0015" feeler gauge in, other 3 intakes will not allow the 0.0025" gauge but will allow the 0.0015". My feeling is at least 3 of them now are very close, if not at 0 clearance. I have a good deal of experience adjusting valves but this is my first time working with shims/buckets. Im really missing the oldschool German style adjustable rockers about now.

I found the slip from last tech, compression/leakdown as follows.
cyl 1 and 2 = 220psi@4%, cyl 3 = 188psi@6%, I believe he performed this right after the last valve adjust.

The milage was not recorded but as I recall there were similiar mild drivability issues so I had that valve adj and comp test done before the stated interval and he said one cyl intakes were running tight. It doesnt seem normal that valves would receed at this rate, it just doesnt seem to make sense that they are ALL tight, not just one or two.

I find this somewhat alarming but is it a common finding? Does it make sense to simply reshim and go on with life? I tend to feel like Im urinating up a waterfall and it might justify a valve job and possibly a re-ring r/t the previous leakdown which certianly didnt improve in the last 10-15k miles. This is my first time in an engine like this so I am appealing once again for wisdom and guidance. TIA for taking the time to read and respond.

Tony

[Shovelstrokeed]

Those numbers make no sense to me.

First of all, 220 PSI would indicate a compression ratio of nearly 15:1 at sea level and higher at higher altitude. Not normal and the bike should be pinging like a bastard with even 93 octane. Even 188 PSI is 12.7:1 and I think that is high for this bike. The leakdown numbers aren't too bad although a difference of 2% from one cylinder to another would suggest a look at that #3 cylinder.

I don't remember any modern engine running much less than 0.006" clearance on the intakes and something like 0.012" on the exhaust. My '67 Bonnie used to run 0.002" on the intakes which was basically a free spinning pushrod with no click. I doubt Triumph carried that old air cooled spec over.

That degree of intake valve recession is certainly not normal at all. I can't imagine anything that could have caused it except a bad set of valves (wrong heat treat) or loose seats.

I would certainly consider pulling the heads and seeing what is wrong. I would look for excessive carbon buildup on the pistons and chambers and quite probably think about replacing the intake valves and certainly recutting the seats.

[Caseyjones955]

Thank you.

I just had to bounce that off someone with Triumph experience. Your wisdom jives with my instinct. The head comes off tomorow if I can find anyone willing to touch it. Can this head be swapped with a Daytona or Tiger head, I believe I may have access to a couple insurance totals?

I ran the snott out of air cooled VW engines, I mean serious missuse and abuse, and never had a whole bank of valves do this, intakes nonetheless. It looks like head removal is pretty straight forward and not a major undertaking. Thanks

Tony