1991 FXRS Lowrider. This morning on the way to work I was cruising about 70mph when all of a sudden "crack" ............"ping, ping ping ping ping ping." I shut it down and swerved to the shoulder. My initial thought was that my throttle cable had snapped (I'm running internal throttle so it has only (1) cable). When I got to the shoulder I still had throttle though. Scooter was still running with the loud "pinging" coming from the front area. When I'd rev the bike a bit the "pinging" would get faster (in sequence with the rpms). My next thought was that I must have broken my front motor mount. Checked it out...............looked OK to me (maybe just needs tightened a bit). Now I started thinking it must be internal. Only weird thing is that the scooter still runs fine...................just has a very loud "pinging" sound. I cruised it down the shoulder in first gear (about 5-10 mph) to the nearest turnoff. Oil pressure is still good. Any ideas? Can a motor still function with a broken lifter, rod, etc? Wouldn't my pressure be considerably affected if it were an internal break?

Thanks

 

Noises are pretty hard to diagnose over teh intr4n3t, yo. If the pinging sounds like metal hitting metal and it sounds external, start looking for it. Front, middle (top) motor mounts, loose tank, fender, etc. can all make weird sounds. Lifters usually sound "knock knock" not "ping ping" if that makes sense. Get a long screwdriver and hold the handle to your ear and go around touching the pointy end to various parts of the bike, frame, motor, etc. until you find the noise. Or buy a "mechanic's stethoscope" from HF, etc. Sometimes you can just start banging on stuff (carefully) with the motor off and hear something rattle. Check your exhaust too.

 

Pull the sparkplug and bore scope it to see if maybe a screw or something went through the intake and is now embedded in the piston and getting pounded into the head. Don't laugh, had a butterfly screw come out once and locked the throttle at full . Knocked like hell too.
Ron

 

thats my thought, maybe a carb throttle screw come undone and got sucked into the engine.

 

look in the exhaust pipes something loose inside ?

 

I've been avoiding this for the past (2) days. After having to drive the truck to work..............I'm ready to get er' fixed. Last night I started it up again. My thoughts are that it definitely sounds internal. I inspected the motor-mounts and exhaust..........looks good. I took a rubber mallet and banged (lightly of course) around on cylinders, heads, rocker boxes, etc..............nothing. Next thing I was planning on doing was inspecting to see if I have a bent pushrod. Seems to me that if I had a bent pushrod or broken valve spring, etc., it would be misfiring like crazy. It runs fine.................just that gawdawful noise.

Then today I checked the forum here..............and the idea that makes the most sense is the following from rbabos & hotrod351:

"Pull the sparkplug and bore scope it to see if maybe a screw or something went through the intake and is now embedded in the piston and getting pounded into the head. Don't laugh, had a butterfly screw come out once and locked the throttle at full . Knocked like hell too.
Ron

thats my thought, maybe a carb throttle screw come undone and got sucked into the engine."

Thinking back I can remember that something sounded like it "came loose" and was "sucked in".

I'm sure hoping that this is not the case.

Thanks again guys.

By the way: I don't have (free) access to a borescope. Would you guys recommend removing the cylinder heads to inspect it as opposed to hauling it into a shop to get scoped?

 

Pull the front cyl top rocker box cover and see if one of the 1/4 in bolts that holds the bottom rocker box to the head came out I've seen this happen twice

 

Well I got the scooter ripped apart saturday. Took out the tappets on the front cylinder and one of them had a bad roller bearing...............which was giving the thing a bit of play........and causing the "pinging" noise I was hearing in the top end. Now that I have everything ripped off of the motor I'm thinking of adding a new cam and possibly an aftermarket ignition to beef up the HP a bit. Couple questions:

1. Andrews recommends a EV3 cam for my FXR............but I noticed that many folks on here are runnin' the E27. Any thoughts on this?

2. Will adding aftermarket tappets increase HP at all? I've noticed folks running the Jim's "Big Axle" tappets............but after doing a bit of research it looks to me like the Jim's is just a more reliable tappet because of the beefier design.

3. Pushrods. I thought that my bike was going to have solid pushrods..........but when I got into it...........it has adjustable. Anyone know if a 1991 FXRS would/could have stock adjustable pushrods?

Thanks -

 

EV27 is a very popular cam (always change the bearing) and unl;ess you want to pull the heads and change springs, stay with a "bolt-in" cam, basically, not over .500 lift.

Tappets will not make any difference concerning power. Big Axle tappets have been known to "trash out" as well - read of several on this site, though I am currently running a set. Stock HD lifters are about 135.00 a set and that's what I will run should these ever give any problems at all.

No, it did not come out with adjustable pushtubes, but they are a good thing. I'm enclosing a link so you'll know how to adjust them according to the thread pitch.

http://www.harleyhelp.com/pushrod.html

 

- thanks alot for that link.

- very good information !

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