How do you know a chain and sprockets need replacing? Chain seems to be stretching regularly

If the chain is stretched, it'll skip, and wear down the teeth on the sprocket. It's best that you get a new chain before you have to replace both sprockets too. This may not be the problem, of course.

looking this up first thing I see this is Not a chain saw ,its a snowblower , you've listed it in wrong category , fortunately for you I fix those too , here's a link to a exploded view of how everything's suppose to fit together , also they sell parts too, chains jumping is most allways a loose /stretched chain ruining a sprocket , they both need replaced
http://www.partsandservice.com/bin/ipl.cgi

Jessica:

First, check the chain and sprockets. Check the two chain sprockets for worn or bent teeth. If either of the sprockets is damaged, replace them. If the sprockets are OK, Check the chain for any damage If the chain is damaged, replace it. You are checking the chain for kinks, stiff links, damage to the link side connectors, and checking that the chain is not bent (side to side) Check to see If the chain is loose. If it is, you'll need to loosen the rear axle nuts and pull the rear tire backwards to tighten the chain, then tighten the rear axle nuts. *Make sure that the rear sprocket lines up with the front sprocket*. Just lay a straight edge along the two sprockets, ( A yardstick will do), and make sure that the sprockets touch the yardstick along the whole length of the sprockets. If the rear sprocket is cocked (not lined up with the front sprocket) loosen the axle nuts again and push on one side of the rear tire or the other side until the sprockets line up.
When you are finished tightening the rear axle nuts, pull up on the chain between the sprockets... the chain should not move up or down more than 1/8 of an inch. The chain will stretch over time, and you need to check the chain for looseness before riding.


Happy and safe riding!

The chain you should be using should be a .325 pitch and not a 3/8.

Never over tighten the chain, it will wear and stretch with time, which is why you should regularly check the chain tension. To get it right you should be able to lift 2 drive links clear of the bar. The chain will naturally wear groves into the spur sprocket, there is no conversion to a rim spricket for this model. Rim sprockets allow the chain to move along the sprocket easier and takes the wear away form the clutch drum.

chech to see that the chain has not stretched too much

Your chain is stretched and needs replaced.
Check your sprockets for wear when you do this.

You may need chain and sprockets.

Keep your new chain clean, and lubricated.

Get the rear wheel off the ground and adjust the chain tension. When checking the tension spin the rear wheel and check that the tension does not go slack or get tighter. If the chain is riding up and down the sprocket teeth then the chain is stretched and needs to be replaced. This is the grinding/clunking noise you are hearing. If the sprockets are worn consider a chain and sprocket set, it can be a less expensive option than buying the parts separately.

You need the pitch, roller width, roller thickness (All in all just the chain type) OEM is a 525, 108 link chain with a 15 tooth front sprocket and 40 tooth rear.
It is best to change sprockets and chain together. A stretched/worn chain will damage the sprockets which in turn will lead to premature wear on a new chain.
Best way to identify pitch(and chain type) is to measure the sprocket width(thickness).

• 0.227" (5.76mm) - 520 chain
• 0.284" (7.21mm) - 525 chain
  
• 0.343" (8.71mm) - 530 chain
  

Technically speaking they all have the same pitch (5/8") as you can see they are of different widths. Please note that a 420 and 425 have the same widths as 520 and 525 but their pitch is different(0.5")
Further you will have to decide between stock, O-ring and X-ring. X-ring being the most expensive(and supposedly longest lasting) but in my experience lasts the same as an o-ring chain.

timing chains in most cases never need be repalced for the life of the engine, timing belts on the other hand last about 60,000-100,000 miles.

Unhook the master link and lay the chain in the concrete. Next, hold one end to the concrete and sort of push the chain towards the stationary end. The object is to push the chain together as opposed to stretching it apart. Mark the concrete at the location of the shortened end. Now again hold the stationary end firm and this time stretch the chain to its' fullest length. Mark the concrete again at the end of the stretched chain. If the distance between the marks is over one inch the chain should be replaced.
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Look at the teeth of both sprockets. Are the teeth rounded on the end or are the teeth forming a pointed looking end? If rounded, then the sprocket is good. If pointed, then the sprocket is bad.
Bad sprockets can ruin a good chain. The exception to the one inch rule is a chain that is rusted and no longer limber. Replace a rusted chain. Remember, always install the master link clip with the blunt end facing the direction of chain travel.
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