Post engine rebuild running issues

[burton1234]

I recently rebuilt my XS 650 engine (first engine rebuild). I only striped down the top end to investigate a tapping noise when the bike was cold upon starting that would go away once warming up after a few mins. I quickly found that the plastic part of the cam chain tensioner was no longer attached which seemed to be the likely cause of the noise. I decided as I’d got this far and had the engine out the bike, I may as well give it a bit of an over hall and repaint.

Everything went fine with the reassembly. The only issue I had was due to now using a PMA Kit I didn’t have a TDC mark to work from when positioning the cam but I was pretty use I had TDC correct.

Once rebuilt and back in the bike, it took ages to first to get it started. And once it was running I really struggled to even idle get it to ideal. I went back to the factory settings on the carb and I’ve tried a multitude of adjustments and I can just about get it to idle ok, but it doesn’t want to rev at all. When I try to rev the bike it spits and sputters and barely revs.

I initially thought the issue might be that I didn’t get the cam in the correct orientation.

I started to strip the engine back down in the bike and have undone and lifted slightly the cylinder head cover. I can see pretty clearly the line on the cam that should be pointing upwards and the dot on the side located correctly when at TDC. Before I go any further stripping and removing the engine does anyone have any ideas of what the issue could be?

I don’t have a timing gun so haven’t checked the timing but as the bike ran so poorly I didn’t think it could be this.

Thanks,

 

[Jim]

I don’t have a timing gun so haven’t checked the timing but as the bike ran so poorly I didn’t think it could be this.

Not sure why you'd think that. Definitely could be timing. Could also be you got a bum PMA. You didn't mention if the PMA also has a different (new) ignition, or you're using the old one?
Same engine, rebuilt.
Same carbs ( I assume... You didn't say otherwise)
New to you alternator (elec power) system.
If it were me, I'd reinstall the old alternator and see how it does.

Would really help us to know what ignition you're running though?
Also, battery or capacitor?

 

[burton1234]

Thanks for the reply.

I am running the standard ignition. I installed a PMA kit from MikesXS for years before.
I have only replaced gaskets and washers etc on the rebuild and the battery with a Antigravity AG801.
Same carbs
I cant seem to find the old alternator at the moment do try that.

 

[Jim]

I cant seem to find the old alternator at the moment do try that.

Well if the battery is nice and full, just disconnect the PMA and see what happens. At least that will eliminate it as a cause.

Maybe drop the float bowels and see if they're all gunked up?

 

[burton1234]

Will do. From what your saying it sounds like it's not an internal issue within the motor itself so I will put that back together and try what you suggested with the PMA.

I took the carbs apart yesterday and they are all clean inside and it still ran the same.

 

[Jim]

From what your saying it sounds like it's not an internal issue within the motor itself so....

You said the cam marks were aligned correctly. So as long as it makes compression the engine should run. Might want to revisit valve lash when you're back together. Other than that, yeah....