Simple fault diagnosing techniques

[knockout_bar]

These are just a rough guide of simple engine faults and how to tell what is making those strange noises.


A "ticking" noise - This most likely caused by your timing is too far advanced, it is called "pinking" (full name is pre-ignition). If left, this can cause major problems, because the spark is firing nearer the piston crown, you run the risk of burning a hole in the top of your piston, which can be quite a costly situation.

A "rattle" (heard coming from the barrell) - This is a sign that your top end bearing needs replacing.

A pronounced "knocking" (coming from the crankcase) - This means your bottom end bearing is gone and needs replacing.

A low end "rumble" (coming from the crankcase) - Your crank bearing(s) are gone and need replacing.


If you're running a two stroke, here are some problems/tips.

If you think that your bike isn't running aswel as it did, the throttle isn't as responsive as it used to/should be.


Help, my bike has no/lost power

1. Is the carb set up right and in sync with the exhaust? - This is a common problem for many people running derestricted two strokes. If the carb is not set up to meet the demands of the exhaust pipe, not only do you loose performance, but you also run the risk of burning a hole in the piston because the engine will be running lean (i.e. not enough fuel). If you think this is the problem, there are two ways of identifying it;

i. Does the bike die with the throttle fully open? - If this is the case, you will need a bigger main jet. Consult your dealer, or one of the guys on here for some advice on choosing the right main jet.

ii. Does the bike refuse to rev up from tickover? - This will be the work of the pilot jet. Again, consult your dealer or someone on here for advice on a bigger jet.


2. Is the air filter element clogged? - This can cause a slightly richer mixture because the optimum amount of air wont be getting through to the carb.

3. Is there a hole in the exhaust pipe? - Engine performance can suffer from a loss of back pressure. If there is a hole, you can either use some exhaust glue (Gum Gun) to patch it up, or weld it up.

4. Are the baffles clogged up? - This can result in a build up of too much back pressure. I can't exactly remember how to clean it up, but you could clean the baffles by leaving the assembly to soak in a tub of petrol (outside). When it's soaked, get at it with an old toothbrush until all the residue is gone. It is also advisable to clean the entire pipe, but I can't remember how to do that (someone here is bound to know).

5. Are the Piston and rings ok? - If your bike has started producing excessive smoke from the exhaust pipe, then it is quite likely that the oil control ring has blown (can be caused by over-revving).

If none of those are the source of the problem, then I would look at the crank shaft oil seals. I would best leave that to the garage, but if anyone is feeling up to it themselves, i'll post how to replace them etc.

Phew, i'm knackered now.

Hope this is of use to someone, and please correct me where i'm wrong. I haven't worked on 2 strokes for a while.
____________________
125 trail bike, custom bars, handguards etc. - ?500.

"egg flied lice" - R6jonny (inspired by McGee)

[Vin]

Symptoms for clogged air filter can be starting without needing the choke up to, in my case, the bike not starting/flooding. Oh and black oily plugs.
Not sure about worn rings on a 2 stroke producing more smoke either. More smoke I do know can be caused by mis firing(any cause) or as you say gearbox oil leaking into the crank case because of worn seals
I don't know about the rest as I am learning as I go at present.
Please don't take this a criticism I am finding this workshop forum really usefull as these issues usually get resolved
So nice one

[knockout_bar]

[Vin]

[veeeffarr]

Might just be me being dumb, but wouldn't you need an Oil Control Ring on a bike who's stroke and oil are mixed automatically and not premixed by hand?

[stinkwheel]

[knockout_bar]

[sickpup]