Hi all. I have a bit of a head scratcher here and I hope you all can help - or bounce some ideas around. Stock cylinders, sent them out to a reputable machine shop with new pistons to have cylinders bored. Everything came back, I put rings into bore about an inch down, measured and filed and measured and filed my rings until I got to the required .018" end gap. Pistons are flat top 10.5:1, cams are Fueling 594's, Fueling race oil pump, heads ported and flowed with O/S valves and high lift springs. I am running a Thundermax on this bike so am able to monitor. Here is what happens: I flashed the Tmax with a close map, initialized the Tmax. While Linked, I started my bike...runs amazing!...for about 45 seconds, then it sounds like it starts to labor for about 3 seconds then dies. While running, the target and the actual AFR are almost bang on to each other, then when it starts to labor, the rear cylinder goes slightly lean and then bike dies. Anyone have any ideas/insight/thoughts?
Thanks.

I posted this in the bagger section and they suggested I post here as well.

Thanks again

 

Once it comes off the cold start mode, it goes lean?
Scott

 

To be honest, no. I can restart it again and it will run again for 30ish seconds and then labor and die. So, here is a question that I have been thinking about. When I was putting everything together, I oiled up my lifters and installed them, but was not able to put my push rods in and adjust them until about 8 or 9 days later due to work. Do you think it's possible that by the time I got back to it, the lifters had bled down completely and i now have overadjusted valves? It seems as though once I get oil pumping through the engine good is when it stalls. I know it's a long shot but my only other thought is insufficient cylinder/piston clearance. This is the only clearance I did not check as I trusted the machine shop to do the correct bore considering they had the piston with them at the time of boring....
I am going to reset the valves and if that doesn't help, I will put a horoscope through the crankcase oil plug hole to see if I can have a look at the bottom sides of the pistons and bores.

 

And no...i will not be putting a horoscope in...i will use a borescope. Silly auto correcting "smart phone"

 

first of all, what is the machine???
if you have hyd valve train, are you using adj p/r's??
if the lifters are full of oil and you have no spring pressure, it will stay forever since there is a check in the lifter (if it holds).
for grins and giggles, let's say the lifters do not pump up, will the engine run??, sure!! there will be a bunch of racket and if you drive it, performance will be down since valve opening is altered. it can take up to 5 miles of riding for a lifter to go functional. i run hyd with S&S spacers and when i adj the p/r, the lifter must be totally collapsed, i adj just enough to quite the valve train, i run high speed and i basically run a solid system, it does alter the cam profile a tad since the grind is hyd.
the ??? is, are the pistons matching the required clearance since diff pistons have diff requirements and if the machine shop was not told (your responsibility) they only did what they were told. should be able to see through plug hole.

 

I agree on all points. It is a 12 FLHX 103" bored to a 107". And yes I agree on the piston clearance requirements and different rates of expansion as well and the machine shop doing as they were told. Bit these were brand new pistons in the box with the dimensions on a card from the manufacturer. I did not state the dimensions. At any rate, I have looked through the plug hole with a borescope and I have seen nothing alarming, but if there is insufficient skirt to cylinder clearance, I may never see any issue on the tops of the pistons, only the bottoms of the bore and the skirts of the pistons No? Correct me if I am wrong(it happens alot..haha), but will the skirts not expand faster than the domes/tops of the pistons?

 

Oh and sorry I missed some points. Adjustable S&S push rods, Fueling hydraulic lifters, and thank you for the info regarding the check ball/valve built into the lifters. I was unaware of that feature.

 

what is your fuel pressure? are you sure you have a mechanical issue, or a fuel delivery issue? hook up a fuel pressure guage and watch it to see what happens when the engine dies,,,,,maybe your fuel pump relay is shutting down for some reason. just a thought, it cant hurt to know what is going on.
m

 

here is the deal with adj p/r's:
the lifter MUST be collapsed, aka bottom of stroke. this way there is no oil cushion. then you must set the p/r so the lifter cup rises to a set point, usually set by counting flats, remember p/r's have diff thread count and varies the lift. if i remember right, i set mine flat wise at around .003 and factor in rocker ratio it would be .005 at the stem. this limits the lifter inner travel just enough to quite the valve train. i do this so there is no start up issues and no collapse issues at speed, hd does not like 6+k rpm.
now if you are not running spacers like i am, then you have a pumped up lifter and adj the cup around .005>.010 (will have to check book) below retainer, cup and retainer must not meet. again, this can be set by counting flats. if this is off then it is possible to extend the valve too far and it is possible that spring pressure drops the small amount when stopped and repeats. the intake is my suspect as it will kill the manifold pressure.

 

The latest...but not the greatest. Rechecked my valve adjustment and reset it to S&S spec of 24 flats beyond zero lash(I had initially set them to 26 flats), checked over everything I could once again, checked fuel tank connector, removed fuel cap in case it wasn't venting properly. Started my bike, runs nice for about 45 seconds, engine starts to labor, then it dies. Start it again, runs for about 30 seconds, labor's and dies. And then the starter begins to have a very hard time turning the engine over. Let it cool down for about 10 minutes, retry starting, it starts reluctantly...runs for about 30 seconds, labor's and stalls, I waited for it to stall, yanked out the spark plugs and immediately hit the starter....the starter is laboring trying to turn over the engine without spark plugs in it. I would say the chances are very good that my clearances are inadequate.... I am all ears/eyes if anyone can think of anything at all that maybe is being overlooked? Otherwise, I will be stripping the cylinders off again. P.S. I cannot see past the flywheels with the borescope and therefore cannot see the piston skirts.