630 super 2, air leak?

[Am leaf]

Figured I'd be in for a carb kit at least as it was stored for a number of years. I'm not sure what else to look for though and would appreciate any suggestions for quality parts. (Canadian if any)

So quick as to the what and why. It's tge model with the 1 fuel line choke lever side.

After tuning it ran fine and an experienced guy said it's OK but could be better. Fine enough to run it. L +1 H +0.5

Filter is clean, undamaged. Plug is used but good blue/purple spark, gap is fine.

Coil gap fine

I keep it very clean but I do like to use the air gun if that's a consideration

Flushed the tanks when I got it, filter seems OK to me, new fuel line was necessary

Cleaned the carb but didn't replace any parts

I'm running mix at 4%, I'm going to switch to 3% though to see how it responds

Will add my mix as of now is over a month old but gas was never in tge saw longer than a week. Will mix fresh gas

During and after tuning I monitored temps regularly and rpm for overspend. I never went wide open for more than 5 minutes straight (firewood), and never without load other than during brief tests as the manual describes. Spark plug was always normal or rich.

I think that's everything, now the how.

Start saw, slight blue smoke after 3 or 4 pulls. Steady idle.

Let saw warm up. Steady idle, no smoke, maybe 3 mins.

Get to cutting, after a couple minutes it suddenly started overrevving. Consistent, no sputtering. Saw was cutting vertically, tip down 45°

Finish cut (2 seconds, maybe 3) come out of cut, saw dies.

Check tanks, forgot to fill them but there was an amount in there, both. Fill tanks, attempt to start, no fire

Check filter, plug, piston and chain move freely, no carbon build up

Attempt again, bit of blue smoke, no fire. Change plug, another used plug but still fine. Attempt again, puff of white smoke

Take a 30 minute break to read on this, come back, compression test 140 psi (with a very old push and hold type with a relatively hard nipple so it might be higher, likely is)

Attempt to start, fire. Hold WOT, won't open up, half speed maybe and 4 stroking with blue smoke. Let off and it dies

Will post any requested pics and appreciate all responses

 

[Am leaf]

Posting pics, screws and gaskets wet, screws were torqued for m5 in aluminum, 15 inch pounds iirc, threads were cleaned, no threadlocker, i believe I installed the screws dry but can't say for certain and I used a small amount of silicone based grease to help hold the carb gasket in place. Slide pn grease I'm pretty sure

 

[Am leaf]

Tested rank case pressure, pressure held for about a half hour, 7psi charge, unable to measure what came out so I'll conduct the test again but leave it for a couple hours. If pressure remains ill basically be at loose screws or carb kit

What do you guys do to make sure the carb screws are tight. I just looked up the torques again and came across a useful link. According to this I've not been tightening these screws at all....

Pic attached as it won't let me post links

 

[ballisticdoughnut]

Have you pulled the muffler to inspect exhaust side of the piston? I’m thinking it’s probably fine but doesn’t hurt to look. You mentioned cleaning the carb but didn’t replace any parts. Order a genuine tillotson kit and replace the gaskets, diaphragms, and needle. Also, when doing a pressure test make sure the saw holds vacuum as well. Generally 7 PSI and 7 inches of mercury.

 

[Am leaf]

Have you pulled the muffler to inspect exhaust side of the piston? I’m thinking it’s probably fine but doesn’t hurt to look. You mentioned cleaning the carb but didn’t replace any parts. Order a genuine tillotson kit and replace the gaskets, diaphragms, and needle. Also, when doing a pressure test make sure the saw holds vacuum as well. Generally 7 PSI and 7 inches of mercury.

Muffler side is fine, I don't want to take my seals off yet otherwise I'd post pics, will do later.

Vacuum I didn't know. I imagine I can rig up something with picrel and a venturi with a valve to test this. Thank you for tge information

Any suggestions on a reputable source for the kit? From what I've seen if can be expensive but if it is then so be it

 

[ballisticdoughnut]

RK-23-HS is the kit you need, just make sure it’s a genuine Tillotson. Generally they’re around $20 freedom bucks. Most saw shops should have them or can get them for you. Or you can take a look on eBay.

 

[ballisticdoughnut]

If it doesn’t look like this, don’t buy it.

 

[Bob Hedgecutter]

All 630's only have the one fuel line and no external impulse line. The 670 and 625 had those, the 630's all impulse through the block- which is notorious for cracking and or bending- causing an air leak.
Pressure and vac test is the only means of assuring air tight condition of seals, O-rings and gaskets, but the old fashioned squirt of brake cleaner around suspect areas can give a hint of where to look.

Mind you, that might not be your problem- 0.5 of a turn out on the H might be.
Piston looks brand new through the intake port- wonder if it looks as nice just off to the side of the exhaust port, clutch cover side of the saw?

 

[Am leaf]

If it doesn’t look like this, don’t buy it.
View attachment 1121377

Noted, 20 isn't close to what I was seeing, ill have a look for this specifically, should get better results

 

[Am leaf]

All 630's only have the one fuel line and no external impulse line. The 670 and 625 had those, the 630's all impulse through the block- which is notorious for cracking and or bending- causing an air leak.
Pressure and vac test is the only means of assuring air tight condition of seals, O-rings and gaskets, but the old fashioned squirt of brake cleaner around suspect areas can give a hint of where to look.

Mind you, that might not be your problem- 0.5 of a turn out on the H might be.
Piston looks brand new through the intake port- wonder if it looks as nice just off to the side of the exhaust port, clutch cover side of the saw?

Clutch cover side, im going to assume that's where the impulse line is. ..

That .5 might be me playing it safe. Tbh im basically learning to drive with dad's GNX.

I'm going to do the vacuum test tomorrow, clean everything as thoroughly as possible and try to start it.

Try to find leaks, propane, brake clean, whatever.

Just got fresh gas. Ordering a carb kit

 

[Bob Hedgecutter]

No, there is NO impulse line- it impulses through the block the carb screws to.

What I am getting at- is at 0.5 of a turn out from seated you might be WAY lean and heat scored the piston and ring which usually starts showing next to the exhaust port on the clutch side of the saw- cannot be seen initially until the cylinder is removed.
But in the meanwhile- add photos of the piston as viewed through the exhaust port with the muffler removed just for kicks and giggles.

 

[Am leaf]

All 630's only have the one fuel line and no external impulse line. The 670 and 625 had those, the 630's all impulse through the block- which is notorious for cracking and or bending- causing an air leak.
Pressure and vac test is the only means of assuring air tight condition of seals, O-rings and gaskets, but the old fashioned squirt of brake cleaner around suspect areas can give a hint of where to look.

Mind you, that might not be your problem- 0.5 of a turn out on the H might be.
Piston looks brand new through the intake port- wonder if it looks as nice just off to the side of the exhaust port, clutch cover side of the saw?

Jut to be clear. 0.5 turns from the 1 turn base setting from the tuning instructions in the manual. So 1.5 turns from 0 for H.

Best pics I could get, I need a bore scope

Seeing this now though that gunk definitely was not there before..but it's also not dried.

Leads me to suspect...idk

 

[Am leaf]

No, there is NO impulse line- it impulses through the block the carb screws to.

What I am getting at- is at 0.5 of a turn out from seated you might be WAY lean and heat scored the piston and ring which usually starts showing next to the exhaust port on the clutch side of the saw- cannot be seen initially until the cylinder is removed.
But in the meanwhile- add photos of the piston as viewed through the exhaust port with the muffler removed just for kicks and giggles.

Ok no, definitely not lean

Settings are from baseline so total is L2 H1.5

 

[Bob Hedgecutter]

Well- yes 1.5 turns isnt 0.5 and thats a safer range- but it looks a bit smeary up that front inner cylinder wall still- so you might be in air leak territory.
Roll the piston down and take a shot through the exhaust posrt that shows the ring and groove.

 

[Am leaf]

Well- yes 1.5 turns isnt 0.5 and thats a safer range- but it looks a bit smeary up that front inner cylinder wall still- so you might be in air leak territory.
Roll the piston down and take a shot through the exhaust posrt that shows the ring and groove.

Posting
What are you looking for? Thank you for your help

 

[Am leaf]

Posting
What are you looking for? Thank you for your help

Forgot to attach

 

[singinwoodwackr]

No, there is NO impulse line- it impulses through the block the carb screws to.

What I am getting at- is at 0.5 of a turn out from seated you might be WAY lean and heat scored the piston and ring which usually starts showing next to the exhaust port on the clutch side of the saw- cannot be seen initially until the cylinder is removed.
But in the meanwhile- add photos of the piston as viewed through the exhaust port with the muffler removed just for kicks and giggles.

Exactly what happened to me with a 670 recently. 1/2 turn out killed it. Rebuild in progress…
oh…50:1 mix ratio, Stihl Ultra…no bueno…

 

[singinwoodwackr]

Forgot to attach

Looks good. What mix ratio?
50:1 and that pic would look quite different

 

[Bob Hedgecutter]

Posting
What are you looking for? Thank you for your help

Looking for marks and indicators in the piston and through the ring.
Looking at that I might suggest the ring has not long been replaced- the scores top of piston from crown to ring groove stop and do not show on the ring.
The photo earlier of the front cylinder wall through the plug hole looks to show possible transfer and or slight grooves- from a lean condition.
So maybe, the saw was leaking, previous owner caught it playing up, re ringed it and sold it on.

 

[hotshot]

Have you pulled the muffler to inspect exhaust side of the piston? I’m thinking it’s probably fine but doesn’t hurt to look. You mentioned cleaning the carb but didn’t replace any parts. Order a genuine tillotson kit and replace the gaskets, diaphragms, and needle. Also, when doing a pressure test make sure the saw holds vacuum as well. Generally 7 PSI and 7 inches of mercury.

Good advise, but 14” of Hg Mercury not just 7…