1975 suzuki gt250: tapping in the engine...help

Okay, so I got the 1975 gt250 (http://www.automotiveforums.com/vbulletin/showthread.php?t=928257) running but, there is a tapping noise in the front of the engine... sounds like around the exhaust ports but I'm not sure, and its intermittent. :confused:

What should I do? Take the engine all apart and look at it? Take off the pipes, run it and listen for the noise? Could it be something in the pipe?s I'm not sure where the noise is coming from.:crying:

Thanks for any advise.
~Zechariah

The tapping might be detonation. Always, always run the highest octane premium gas you can find in air-cooled 2-strokes like yours. Regular gas makes these things rattle like pebbles in a blender.

It also might be a blown head gasket. When the engine is running place your hand around the cylnder head where it meets the engine. Do you feel any puffs of air? If yes, the head nuts may just need retorquing.

There are very few moving parts in your engine, so there is not much to go wrong.
These engines are made with lots of piston clearance when cold (to allow for thermal expansion) so you are apt to hear some piston slap until it's fully warmed up.

Also air-cooled 2-strokes tend to wear out quickly too, so often there is piston slap anyways. They benefit from new rings, new pistons, and re-honed or rebored cylinders as required.

So... up to a point, some tapping noise is acceptable and normal for 2-strokes that show some wear. They don't call then "ring-dings" for nothing. (http://www.lacar.com/lenfrank/ring-rin.htm)

BTW 2-strokes run very badly, if at all without exhaust pipes. Taking the pipes off will likely not tell you anything.

A bud's bike had a weird sound almost like valve noise but not quite sometimes, under certain loads. Turned out the header pipe collet was bad on one exhaust port...pipe would rattle around if the vibration was just right...

Worth a look..

I agree with Jeff. Most every ticking noise I've ever heard on a 2-stroke is due to an exhaust leak where the pipe meets the cylinder head.

Alright, thanks for the reply's guys.
My father came out and listened to it and said it sounds just like the one he had about 20 years ago. It is really neat that we found this bike it's the same year make and model as the one he bought right after he got out of high school :smile:.

Okay so the only other I need to do is set the points and idle just right. :confused:
I took some pictures:
http://gladshopper.com/pt2/Suzukigt250pointsA.jpg

http://gladshopper.com/pt2/Suzukigt250pointsB.jpg

and I'm wondering if any one out there has a good running 1975 Suzuki gt250 that could be so kind to take pictures just like these so I can tell just where to set the points, and idle.

Or if anyone just has info on how to set them then that would be great. :smokin:

Thanks,
~Zechariah

It might be time to check Ebay or some place for a Haynes or Chilton manual for this model.
Tuning the carb and mixture on 2 strokes is a bit of an art. You need someone who is experienced in 2-strokes to ride it. By sound and feel you can tell if its too rich or too lean and adjust accordingly. There really is no 'factory' adjustment that suits all bikes. So we can't really help you on that.

I think the mixture screw on the carb is just the idle circuit. I think (but am not sure) The main jet is adjusted by removing the top of the carb and raising or lowering the main jet needle.

Those look like mixture and oil injection ratio screws...not idle..be careful

Those look like mixture and oil injection ratio screws...not idle..be careful

The big one on the left is mixture, (probably the low speed mixture, not the main jet).
The one on the right is idle speed.
All Suzuki injector systems back then (called "CCI") were pre-set and had no adjustment, as far as I know.

I do agree... be careful. Don't tune the knobs unless you have an experienced buddy to give you guidance.

http://www.ridermagazine.com/output.cfm?id=2155213

You can now special order a genuine Zuk manual ^^ Check out the link above.

For longevity's sake, I would also eliminate the auto oiler and premix the oil and gas. I'm not sure about the Zuki system, but Yamaha's oil injection system back in the 70's was junk. My old DT125 Enduro went through 2 pumps under warranty when it was new, (my dad originally bought it for my mom to ride, but she didn't like it) and even the dealer suggested bypassing it and using pre-mix. Just a suggestion from experience on another make and model, so if any of you Zuki people know different, please feel free to correct me.