Forum

[mechguy79]

Hello all,

I need some help with a buddy's Classic 500 military edition. I'm not a Enfield guy but do my own wrenching when able.

Symptoms: Hard miss/studder under any load. It's crazy how bad it is. It will studder before you fully release the clutch on acceleration. Engine sounds very knocky. I don't know how else to explain it. I've had my fair share of 4 stroke thumpers and this thing is so loud in comparison. Here is a short video with summary and engine run:

https://youtu.be/bWF-YgpvQ-k

Engine always starts right up. Idles fine. Currently have an O2 sensor issue and waiting on parts, but engine light is recent, the hard studder is not. Unplug the O2 sensor, no change. It's gotten progressively worse over the year since my buddy has owned the bike. It is now unrideable.

I've change spark plug to the recommended NGK, gapped correctly. Reattached plug cap and coil side. Pulled fuel pump, checked what I could. Nothing found. Tank is clean. Pulled injector, looked clean, sprayed great. Cleaned anyways. Fuel pump primes fine. Cleared engine codes, O2 blink code returns. No vacuum leaks after doing a carb spray test. TPS is secured (didn't move it). Battery is strong. Checked for frayed or rubbed wires. Nothing so far. Plug color on old plug looked great. Blueing on header pipe. Exhaust pipe tight with recent exhaust gasket change. Muffler tightened and no exhaust leaks.

Studder remains. I've tried all the easy stuff I can think of. I don't have any kind of scanner to monitor ECM and read sensor data. Don't know if that is a thing on this bike. I can on my Triumph, which is very nice. Any help is greatly appreciated.

[Daiwiskers]

As I don't have a computer only my phone everything sounds bad

But I would get a stetherscope (spelling) or a thumb over a screwdriver end stuffed in your ear out and try to track down the knock it could be valve train noise or something in the bottom end

Try to track down the knock would be the starting point for me

Hope this help's Dai

[Vince2]

Hi, I had something similar on a bullet, a defective regulator was putting to much charge to the coil. It felt like the engine was trying to run backward with lots of lurching. At idle with low charge it ran normal. Try running with alternator disconnected. Vince

[Haggis]

Sounds like bad hydraulic follower.
If they don't hold pressure they are very noisy.
When you say you adjusted the tickover?
With the large brass air bypass screw screw., NOT the one on the throttle body butterfly next to the cables.

[mechguy79]

I didn't adjust and of the indicated screws. I adjusted the set screw directly on the throttle. Bottom left by the thumb. Didn't notice the large, brass looking flat head screw. I assume that's idle air adjust?

Anyways, thanks everybody for the ideas. I'll start going through them, starting with the charging system. Didn't think to check that.

[Haggis]

That small screw has yellow security paint on it to warn anyone not to touch it.
The screw is set to hold the butterfly at 5° open (afaik) and the throttle position sensor is set to 0.6v output.
You need to try and put it back to where it was otherwise the ballance between throttle opening and the voltage from the tps are not going to match.