Useful suggestions are welcome for a complete overhaul - Castor CP 500

[lecbr600]

I'm a heavy reader of this forum but, caused I'm not a english native speaker, I posted very few posts. This time I'd like to ask some useful tips about a major overhaul I'm performing on my Castor CP500 chainsaw.

Let's start from the beginning.
The reason I decided to perform such a task on my chainsaw is an air leak I noticed last time I was cutting firewood: chainsaw would not rise rpm when I squeezed throttle, then almost impossible to adjust carb as the symptoms remained; and at the end as I tilted my saw to the left/right, idle rpm started increase!

So I decided to replace oil seals, rebuilt carb, and so on. Removing the old oil seals has been almost impossible for me: I tried a lot of stuff, but without any success. So I decided to split the engine and carry out a complete overhaul.
Disassemble was pretty easy, but I found some surprises on which I'd like to recevice some tips from you.

Inspection results

1. Rolling bearing must be replaced as they run, by hand, very bad. It's very surprising to find out only after disassamble that bearings are to be replaced.
2. Piston. I realize that all the symptoms my saw was showing are to point a lean running way. But I stopped pretty early in order to avoid any further damages. So after inspecting piston, I've found a couple of some scores on the skirt together with some black carbon dust on the top and heavy brown color on the skirt
   
3. Cylinder shows a very small scratches (only a couple). Touching them by finger I cannot feel nothing

Cylinder exhaust side view

Cylinder inlet side view

Cylinder


Piston exhaus side



Piston inlet side


Piston inlet side and top view



My questions are:

1. Do I need to replace the piston?
2. Piston ring and cilinder clearance: I measured about 0,50 mm at ring tips once inserted inside the cylinder (45 mm piston diameter). Do I need to replace the piston ring?
3. Why so much carbon buit up? Maybe of my 3% oil/fuel mix?

Any suggestion is welcome

 

[Big Block]

If you can I'd replace piston and ring. Clean the jug. Then port it whilst it's apart

 

[lecbr600]

....
Then port it whilst it's apart

Port it?? I have absolutely no idea how to do that! [emoji15]

I think to leave it at its design state...



Inviato dal mio Moto G (4) utilizzando Tapatalk

 

[Big Block]

Port it?? I have absolutely no idea how to do that! [emoji15]

I think to leave it at its design state...



Inviato dal mio Moto G (4) utilizzando Tapatalk

At least through it back together with out a base gasket for a little more power

 

[grack]

I'm a heavy reader of this forum but, caused I'm not a english native speaker, I posted very few posts. This time I'd like to ask some useful tips about a major overhaul I'm performing on my Castor CP500 chainsaw.

Let's start from the beginning.
The reason I decided to perform such a task on my chainsaw is an air leak I noticed last time I was cutting firewood: chainsaw would not rise rpm when I squeezed throttle, then almost impossible to adjust carb as the symptoms remained; and at the end as I tilted my saw to the left/right, idle rpm started increase!

So I decided to replace oil seals, rebuilt carb, and so on. Removing the old oil seals has been almost impossible for me: I tried a lot of stuff, but without any success. So I decided to split the engine and carry out a complete overhaul.
Disassemble was pretty easy, but I found some surprises on which I'd like to recevice some tips from you.

Inspection results

1. Rolling bearing must be replaced as they run, by hand, very bad. It's very surprising to find out only after disassamble that bearings are to be replaced.
2. Piston. I realize that all the symptoms my saw was showing are to point a lean running way. But I stopped pretty early in order to avoid any further damages. So after inspecting piston, I've found a couple of some scores on the skirt together with some black carbon dust on the top and heavy brown color on the skirt
   
3. Cylinder shows a very small scratches (only a couple). Touching them by finger I cannot feel nothing

Cylinder exhaust side viewView attachment 575094

Cylinder inlet side viewView attachment 575095

Cylinder View attachment 575096


Piston exhaus side
View attachment 575097


Piston inlet side
View attachment 575098

Piston inlet side and top view
View attachment 575099


My questions are:

1. Do I need to replace the piston?
2. Piston ring and cilinder clearance: I measured about 0,50 mm at ring tips once inserted inside the cylinder (45 mm piston diameter). Do I need to replace the piston ring?
3. Why so much carbon buit up? Maybe of my 3% oil/fuel mix?

Any suggestion is welcome

Welcome i have several of the alpina castor saws excellent saws the coils suck though i need coils for my 540i and 600p the pro 41s have been great saws.
I don't have one like yours though.
Do you have a picture of the whole saw.

 

[lecbr600]

Do you have a picture of the whole saw.

No, I'm sorry! Now my saw is all disassembled!
Once all overhaul is finished, I can send you a picture.

Antonino Leone




Inviato dal mio Moto G (4) utilizzando Tapatalk

 

[grack]

No, I'm sorry! Now my saw is all disassembled!
Once all overhaul is finished, I can send you a picture.

Antonino Leone




Inviato dal mio Moto G (4) utilizzando Tapatalk

That's ok i thought you might have a few lol
That's what we usually do is keep saws we like and spares
Is alpina still a presence there i always liked thier saws and still use them and the vip 25 brushcutters i have 4 lol

 

[Chainsaw Jim]

Do I need to replace the piston?

Absolutely not. Most of the knurling is still visible so it only needs cleaned up.

 

[Little Al]

Piston's fine a clean up & new ring, clean cylinder & you are good to go. I don't know of the parts availability in Italy, but in France they are difficult to get Motoruf .com will more than likely get you an IPL to download & they may have parts If you are looking to gain a bit more power this saw responds OK to a muffler mod the porting is not going to give you much gain Shame they are not more widely marketer ed as they produced some good saws esp the Prof Range

 

[Conquistador3]

I don't know if this can help you but your saw is a rebadged Alpina P500: engine spares for that series are becoming extremely difficult to find. Oil pumps, starters, coils etc are still relatively easy to come by.
I'll ask the local ex-Alpina dealer if he still has something left over (he switched to Hitachi/Tanaka last year) but I wouldn't hold my breath.

 

[lecbr600]

Thank you all for your replies... I appreciated all a lot!

Just to keep you updated on the final test after rebuilt the saw.
What I did, at the end, was:

1. Clean piston and cylinder
2. Replace piston ring (new one has 0,20 mm clearance, old one about 0,50 mm). Before doing this task I took care of clean the ring seat!
3. Change rolling bearing and oil seals;
4. New gasket for cylinder and engine carter;
5. Fuel tank cleaning and new tube;
6. Carb rebuilt, with new gasket and membrane.

So, I bet you'd think that the chainsaw was fine. NOT.
It keeps on not rise rpm. It is only possible to run with cold starter activated, and, as it gets warmer, close the "cold starter", but is it impossible to squeeze the throttle.
Saw respond well to Low carb adjustment, but no response to High adjustment.
So, I though that the fuel not reach the engine:

1. I removed the fuel filter inside the tank, and made a test run. Result: not effective
2. Then I tried to remove the carb, clean it again by compressed air on every single orifice, on the L / H jets, insed the throath of carb. Result: not effective

Now, I don't know what to do!!! My last suspect is that inside the H jet should be a sort of check valve, that is underneath the H welch. I suppose that there is some clog in it, and it can explain why H adjustment is not effective.
To perform such a task it is necessary to remove the H welch, but I never done it and I don't know how to do.


One more question: What is the model of my carb? WALBRO WT 419 or WT 715???


As usual, your suggestions are welcome.
Thank in advance

 

[pioneerguy600]

Walbro WT 429

 

[pioneerguy600]

I would suggest just getting a new replacement carb in this instance unless you just want the challenge of working on this carb, the carbs from China are fine in most cases and cheap. Not sure what a new WT 429 would cost over your way but around my location it runs close to $100.

 

[lecbr600]

Very good suggestion! I appreciate it a lot!
But I don't know where to start my search, and I don't know how to look for a chinese carb (model for instance...)

By the way, today I've asked for a new WT 429A. It costs 104 euro!!!!

 

[lecbr600]

I've done!

I'd like to share with all of you my experience, now that I've fixed my chainsaw.

1. I'd done pressure test of carter: Ok, no leaks detectable
2. If it is not air leak, must be carb issue

Then I started to disassemble again the carb, this time I decided to remove the H welch, because this time I wanted be sure that EVERY thing were right. Remove H welch is not an easy task; it may be dangerous, as the risk to damage cast and orifice is very high. Lucky, I succeed to remove and.... the capillar screen that is under that welch was clogged!!! I've got it!!!
So, in the Walbro K20-WA kit I've found both new capillar screen and new welch. So I replaced all if them. Only now I can say to have accomplished a complete overhaul of carb

Now the chainsaw run fine, very easy to carb, and starts soon...

CONCLUSION: If the carb diaphram replacement does not fix your issue, start thinking of H capillar screen. I know it is not an esay job, but consider it as a last change before replace the entire carb. That's my experience

Regards