I laid my hands on this 2nd hand 2017 Shindaiwa 251Ts, mainly as a test case, before I ventured into porting my new Echo 2511wes. Eventually the porting went just fine (on both), and the engine actually showed to be in pretty good condition, running just fine. So now I'm keen on getting some use out of it. But I run into this chain tension issue, when I tighten on the chain cover, the chain doesn't run smoothly and feels as if it's somewhat jammed up by some sort of friction, whether caused by the chain or the sprocket.... I assume the chain, but that's unclear.
Just for the record, I do know how to tighten, and not to overtighten a chain. But after putting on the chain and tightening the cover, then trying to spin the chain by hand, actually needing to use the screwdriver of the spark plug key, the chain is felt grabbing every sprocket tooth and needs some force to have every drive link grab and get past a sprocket tooth. So instead of spinning freely, the chain is forced forward in bumps.
The chain break is obviously off. There's no debris blocking the chain. The entire saw was cleaned up while disassembling for porting. The clutch sprocket has the normal play to run freely without a chain. The bar sprocket runs freely. The sprocket/chain/bar match. Mounting a 1/4" sprocket/B&C, or a 3/8" setup with 1.1 or 1.3 links, the issue persists. Switching these onto the Echo 2511, those setups work just fine. I've quadruple checked not putting a faulty combo of sprocket/B&C on the Shindaiwa.
I mounted a brand new 3/8" OEM sprocket, because the old one it came with was quite scored. This new sprocket is quickly getting slightly scored too after a few runs, while tuning the engine post modification, as it needs to force the chain on its way. The scoring on the old sprocket was probably mainly due to this preexisting problem.
Following the chain passing under the mounted chain cover, it shows a clear path to and from the sprocket, and doesn't look pinched by the cover nor the body. When exchanging the chain cover with the new cover of the 2511, the problem persists, excluding a break issue or a pinching cover.
The body of the saw isn't deformed, cracked or damaged whatsoever. The metal chain plates on the body or the cover aren't deformed, either, although showing some normal use wear. The bar screw and stud are snug on the body and have no play in them. The bar stud shows some wear, giving a mounted bar some upward play, which could (over)tighten a chain pushing the bar through a cut. However, the problem persists when there's no strain on the bar and shows by just tightening the chain cover.
Trying to wiggle the fly wheel or the crank on the clutch side shows no play and feels real snug, and there's no particular noise from the crank shaft bearings. The sprocket is mounted as per manufacturer's indications: black washer > oiler worm drive > needle bearing (greased) > sprocket (new, fitting in the oiler drive protrusions) > washer > clutch. All parts in good condition.
In the current situation, using the saw would probably need me to put on a new sprocket every week. Even if this saw was initially meant to be a porting exercise, I'm very curious into the cause of this problem. As I'm out of ideas, perhaps someone here has a clue what to look for?
Just for the record, I do know how to tighten, and not to overtighten a chain. But after putting on the chain and tightening the cover, then trying to spin the chain by hand, actually needing to use the screwdriver of the spark plug key, the chain is felt grabbing every sprocket tooth and needs some force to have every drive link grab and get past a sprocket tooth. So instead of spinning freely, the chain is forced forward in bumps.
The chain break is obviously off. There's no debris blocking the chain. The entire saw was cleaned up while disassembling for porting. The clutch sprocket has the normal play to run freely without a chain. The bar sprocket runs freely. The sprocket/chain/bar match. Mounting a 1/4" sprocket/B&C, or a 3/8" setup with 1.1 or 1.3 links, the issue persists. Switching these onto the Echo 2511, those setups work just fine. I've quadruple checked not putting a faulty combo of sprocket/B&C on the Shindaiwa.
I mounted a brand new 3/8" OEM sprocket, because the old one it came with was quite scored. This new sprocket is quickly getting slightly scored too after a few runs, while tuning the engine post modification, as it needs to force the chain on its way. The scoring on the old sprocket was probably mainly due to this preexisting problem.
Following the chain passing under the mounted chain cover, it shows a clear path to and from the sprocket, and doesn't look pinched by the cover nor the body. When exchanging the chain cover with the new cover of the 2511, the problem persists, excluding a break issue or a pinching cover.
The body of the saw isn't deformed, cracked or damaged whatsoever. The metal chain plates on the body or the cover aren't deformed, either, although showing some normal use wear. The bar screw and stud are snug on the body and have no play in them. The bar stud shows some wear, giving a mounted bar some upward play, which could (over)tighten a chain pushing the bar through a cut. However, the problem persists when there's no strain on the bar and shows by just tightening the chain cover.
Trying to wiggle the fly wheel or the crank on the clutch side shows no play and feels real snug, and there's no particular noise from the crank shaft bearings. The sprocket is mounted as per manufacturer's indications: black washer > oiler worm drive > needle bearing (greased) > sprocket (new, fitting in the oiler drive protrusions) > washer > clutch. All parts in good condition.
In the current situation, using the saw would probably need me to put on a new sprocket every week. Even if this saw was initially meant to be a porting exercise, I'm very curious into the cause of this problem. As I'm out of ideas, perhaps someone here has a clue what to look for?
