Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Another M3W Exhaust Supplier

I have used 5/16-24 UNF Kaynar nuts MS21042-5 from LAS Aero. https://www.lasaero.com/products/article/CUB8AQL The gaskets look like the correct type but I have usually got them from a Morgan dealer at a surprisingly good price.

nice color on those jetnuts. i just used black anodized ones but the gold would have looked better with the titanium wrap.

Jonathan G

The exhaust gasket I used was an S&S 106-5029, different than the link you shared.

'Proper' Kaynar nuts are the ones to go for. MS21043-5 are the high temperature rated version so ideal for our application.



Like the ones Planenut recommended, they are self-locking so no need to use the locking tab washers that MMC use.

Of course, being cadmium plated those kaynuts are not road legal
We're running silver plated ones. More bling, less toxic, and higher heat rating

I would get out more, but I'm too busy poring over thread standards...

Well to be honest the ones I really used are very eco friendly and re-cycled as they came off the turbine case of a dead jet engine, I assume the heat rating is OK as well 😁. I will update the number in the next Alternative Parts List to MS21043-5, we need plenty of bling 😊.

For exhaust gaskets James Gaskets also makes an excellent crushable copper O ring style which I have better luck with in regards to sealing than the woven stainless/graphite ones. Not to be confused with solid copper gaskets, these gaskets are a copper wrapped stainless mesh type, so a nice degree of crush available.

Part number is JGI-65324-83-CG, for 1984 and newer Harley EVO motors. Hold them in place in the head with a small dab of grease when mounting the pipe.

Hopefully the last question on this little saga. Since drilling out the baffles and fitting the G56 air filter cover this car is struggling to start. Yesterday morning it struggled backfired once and then started. Did a 15 mile trip and wouldn't restart for 45 minutes. This morning it started but again struggled. Could these changes have affected it? Oh and battery is in perfect condition.

Opening the exhaust and fitting the air filter cover would certainly not cause this behavior. Something else is amiss, coincidentally.

Unfortunately it's all but impossible to diagnose these things from afar. A few likely culprits though, might be lack of fuel pressure (i.e. a failing fuel pump or plugging fuel filter, which sets the system pressure), the crank position sensor, or loose plug ends.

You can check the first by turning on the key (don't start the engine-accidentally spraying fuel over a hot running engine is not recommended) and measuring the pressure at the schrader valve on the injector housing on the right hand cylinder. A regular air pressure gauge can be used in a pinch, though it will of course become gasoline soaked. You are looking for 58psi there.

Crank position sensor testing is covered in an earlier post on this forum that I can't seem to find at the moment. I've never had to check one personally.

Loose plug ends (the small threaded bit on the top end of the plugs) are common on this high vibration engines, but are easily fixed by crimping them tight with pliers or the use of a liquid thread locker (Loctite et al).

I'm sure others will chime in with additional ideas as well.

I doubt that drilling out the exhaust baffles and changing the air filter would cause this problem. Maybe something altered when fitting the filter such the throttle not hitting the closed stop, or throttle position sensor moved, Idle Air Control Valve disconnected? When it does run, does it run well as normal or lumpy? Possibly dislodged an inlet O ring seal? The adaptive maps will take a few miles to adapt to the new set up but that shouldn't have any effect on the starting. Unrelated but check the plug caps are tight as that just takes a few seconds and causes many starting and running faults.