Can I Run 3/8 LP CHAin on an Echo CS490

[blueacre]

My son recently bought an Echo CS490 with 18 inch bar. Seems like a real good saw so far. Fairly light but decent power. It comes stock with a .325 chain. I have about ten 3/8 LP chains I have collected over the past 30 years from several Poulan and Homelite saws - two of the chains are brand new and at least 4 of them have minimal use - probably 80% life left. I bought an Echo CS590 last year and retired all my old budget saws so have no further use for the 3/8 chains also have a couple nearly new 18 inch matching bars from the same saws.

Wanted to see if we could use the 3/8 chains on the cS490. I found a few posts online with some info on getting a special 3/8 rim sprocket and modifying the bar mounting holes and possibly the chain length but the one link I found to a sprocket for the swap didnt work.

I looked up the CS490 on the Oregon website parts finder and it shows the replacement for the .325 OEM Rim Sprocket for this model is Part #11892. Specs on this sprocket are 7 teeth with an SM7 mounting spline and has a radial port (says that helps to throw off sawdust and debris).

I searched the Oregon site for a 3/8 sprocket with the same mount - found Part #18720 which is a Rim Sprocket with 7 teeth, SM7 Spline Mount Size but has no radial port. Copies of info from Oregon website attached.

It looks like the 18720 sprocket should fit on the CS490 since it has the same SM7 spline mount but I am not sure whether having no radial port makes it a no go to use on the CS490 or if it is just a nice to have?

Assuming the lack of radial port isnt a showstopper is there any reason why the 18720 sprocket cant be used on the CS490 to run the 3/8 chains with the appropriate bar and chain length modifications ? Any comments or additional info on doing this chain swap will be greatly appreciated.

 

[Franny K]

The radial ports are kind of holes or depressions from the circumference at the middle of the drive link hole. The 3/8 sprocket is larger in diameter and will have cut outs on on side for tree parts to get out of the way. Same thing with the 9 tooth 1/4 small spline sprockets, the Oregon ones will be radially ported. The small spline is as large as possible for a .325 chain's drive links, 7 of them, to fit. The 3/8lp chain really should have a somewhat larger sprocket than full sized 3/8 and currently only Stihl is offering that and not in the spline size you have or can get into easily. Then there is what the manufacturer recommends for max cc for 3/8lp.

 

[blueacre]

thanks for the reply Franny K - I am not clear when you say the 3/8lp chain should have a larger sprocket than full sized 3/8. I though the drivers were larger on the 3/8 full size chain and a lp chain would go on a full sized 3/8 sprocket but not the other way around because the full size 3/8 drivers would bottom out on an lp sprocket ?

 

[esean]

Might want to see if you can find the Stihl 23RSPro narrow kerf .325 chain. It is available in the U.S. in some areas. Reportedly faster than 3/8LP. Even if you do find a way to convert to 3/8LP, those old chains might not be worth the effort. Stihl PS/PS3, on the other hand, should work great on that size saw.

 

[Franny K]

The 3/8lp and the standard 3/8 chain both have 1640 drive links per 100 feet. So rivet center to rivet center is the same. The rivets for the 3/8lp are closer to the sliding surface of the bar and the contact points on the drive sprockets hence the drive sprocket should be larger. What happens is the chain is pulled by the first tooth that engages it, and a bit of slippage at that, and really is loose the rest of the way around the sprocket. It kind of bangs up the drive links. I guess it depends on how much this annoys you. I suppose one could rationalize that if Oregon chain 91vxl for instance is rated to 42cc that is likely for a six tooth sprocket so going to 7 would be less tension and more speed so 50cc is OK. Could kind of look at it that way. The Stihl Picco chain is more robust if you take it apart and measure things.

 

[TNsawman]

I have run 3/8 LP with a standard 3/8 rim on a 490, but only for a limited time, so I don't know how it beats up the drive links if any. Oregon bars with a part number ending in 041 should fit as far as I know. You should check to make sure oil can get where it needs to or drill holes if it needs separate oil holes. I don't think I had to drill holes on the 20" bar I used which was the longest 3/8 LP 041 mount bar I could find. I have also run a 12" 1/4 on a 490, and again can't remember if it needed unique oil holes. Small spline rim is what you want to fit the 490. Stock Poulan chains (poulan SKIP chains) may not perform all that well having so few of teeth and some having lots of safety bumpers.

I do know you have to watch out for brand compatibility sometimes. Some brands of 1/4" pitch are not compatible, while some will work well enough even though it's not a perfect fit. I think the same goes for mixing 3/8 and 3/8 LP. The non LP sprockets tend to have sharper teeth I think.

 

[blueacre]

Thanks for all the info and pictures Franny K - that explains the larger diameter sprocket for the 3/8lp.

Also thanks TNsawman for your info. I figured may have to do some work on the oil holes id I try to use one of the bars I already have but wanted to make sure I could find a sprocket that would work on the 490 saw with my chains before I worried about that.

The chains I have are Oregon S62 Advance Cut 3/8 lp .050. I have 2 brand new and 4 nearly new chains and dont have a running saw to use them on. Not worried if the 3/8 sprocket beats up the drive links a little since I have no other place to use them as long as there is no chance of damaging the 490 saw - only has about 5 hours on it. When cutting firewood with my son my 590 usually does all the cuts on the big stuff and the 490 is used for the smaller limbs so if the chains are less aggressive cutting that may not be too bad.

 

[blueacre]

FYI, found a PIcco chain sprocket that fits the Oregon small spline on my CS490. My understanding is Stihl PIcco is the same as 3/8lp so should work with the chains I have. Sold by
6K Products, 1006 143rd Ave, SE, Tenino, WA 98589, 360-264-2141. Part # DS0252 - $27.72 plus shipping. They also have several other sprocket tooth counts for the Picco chain - to fit Oregon small and large 7 spline applications - see https://www.6kproducts.com/sprocket-375_p_pitch.html

 

[Blackgmc99]

FYI, found a PIcco chain sprocket that fits the Oregon small spline on my CS490. My understanding is Stihl PIcco is the same as 3/8lp so should work with the chains I have. Sold by
6K Products, 1006 143rd Ave, SE, Tenino, WA 98589, 360-264-2141. Part # DS0252 - $27.72 plus shipping. They also have several other sprocket tooth counts for the Picco chain - to fit Oregon small and large 7 spline applications - see https://www.6kproducts.com/sprocket-375_p_pitch.html

How did you make out with this project?

 

[stubnail67]

Been out of the chainsaw addiction for a bit but why not get a rim instead of a sprocket? way cheaper....Its been a few years but i remember when i bought mine/490 one of the other members was really happy with a 3/lopro rim he had custom done by another member... Me i just went with a muffler mod and the narrow kerf it cuts good enough.... I do have to say i have way more lo pro chains then the narrow kerf .325.....But these days im collecting fishing tackle LOL Tight Lines!

 

[Piotr Pakula]

It has many advantages and only one disadvantage will stretch faster. If you cut a little for yourself, you will not feel this defect