The fixed jet being the high speed jet, i would run it and see if it runs peoperly. As long as its "4 stroking" out of the cut, and running good, i wouldnt mess with it.
McCulloch Chain Saws
- Thread starter Bruce Hopf
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They are marked/ stamped. I believe mine was 25 which is probably a reference to a thousandths or a drill size.
According to bob johnson, it is reference to thousandths. Ive asked him that before. He did not think he had any jets to change and told me it would be likely easier to find a different carb. To put on the saw.
Well you could always drill it.
kbeck
ArboristSite Member
Thanks will get her cleaned and go from there
Did not get to cut any Saturday so I cut some today. A neighbor called today and asked for help felling and bucking a oak. Here is a
picture. Cut most of the day with the PM805 and the PM10-10S and some with the MAC140.
Brian
picture. Cut most of the day with the PM805 and the PM10-10S and some with the MAC140. Brian
I've got a tilly fixed jet that runs great except... it's very lean on the high its barely four stroking at all I have no rebuild kits for tilly's so haven't touched it but is there some reason why its running lean? Can I adjust the metering lever to sort that?
I end having to run the low quite rich to get it almost ok but still not good enough
Screwbolts
Never to many Engines!!
What model is your Tilly?
It is possible that under the metering diaphragm there is a jet in the high speed circuit that could be opened just a tad with a jet drill. The metering lever will/should only control the amount of fuel available on the metering side of the carb and should have no effect on the HS fixed jet. Untill you get the lever to high then you will pump fuel straight threw the carb with every piston pulse.
I have a couple fixed tillotsons in my carb box, you have made me curious, I am going to go see what makes them tick.
Hey man good to see ya over on the yellow page. I'm pretty sure it's a hs160 u could be wrong though.
I thought that was the case with the metering lever but I do hear of carbs running to rich and dropping it a touch helped.
I really have no clue carbs are not my thing at all. Fossil helped me learn to put kits in them and pull the welch plugs but that's about the end of it for me haha.
Can tune a saw though
Honestly Jethro any compensation modifications that would help require that you take the carburetor apart. In the process of taking it apart you might screw a gasket or the diaphragm and without a kit on hand ,well the saw won't work at all then.
Micro drill bits are the key to modifying any carburetor and a set point to which you can return.
Under the large welch plug (sdc)there are transition fuel holes or ports that feed at a timed rate based on the throttle plate, (these are called transition slots on a Holley 4 barrel and are on just about every carb you'll ever see in one form or another)with the welch plug removed watch holes and slowly open the throttle by hand with a light shining down the venturi the first hole is exposed then the second, ( some carbs have 3) those ports keep the saw from stumbling when cracking the trigger wide open. Drilling the latest opening hole "thousandths" slightly larger would have a richer affect on the mix, or drilling the brass insert jet that has no metering screw, but go too big and it will be pig rich.
Guys have soldered jets closed and reset the factory hole or epoxied them shut but the taper of the hole has a big effect on fuel speed delivery.
Having a stash of carbs to experiment on is also good.
That's exactly why I've never touched it have no kit and have been running SDCs instead and have some kits for them.
Another thing about the carb in question it slowly got leaner and leaner each day I'd use it I'd have to keep cranking the low to keep up until it got to far. So I suppose something could be blocked up but yeah no kit so never touched it.
Tell ya though they run dam nice on the tillotson seems more sporty than the sdc65 it got swapped with (rebuilt) it runs perfectly on it but just different.
The 44s seem to run better and get that sporty feel again
Screwbolts
Never to many Engines!!
Hi Jethro, what model funny color Yellow and Black saw are you tinkering on? LOL I have quite a few extra Tillotson carbs kicking around in my carb box. I to like Tilly carbs, man you got me doing It to. (Tilly). LOL. I also know I have at least 2 complete kits in the drawer.
A nice old 7-10. Dam good saw too.
Never had any other "tilly" experience other than 7-10s got another that runs amazing on 1
That's seems a little suspicious right there. You could be correct that there's some debris congestion in the jet. Think I'd be looking for an air leak getting progressively worse as another more likely possibility.
Screwbolts
Never to many Engines!!
MS has given you good tips.
If you had a kit you could clean your carbs HS jet without removing it or doing damage to it, by boiling the carb body in plain old WATER. First you would strip the carb of gaskets and diaphragms, and the LS needle and the Main metering needle that the fulcrum hooks into. Boiling water is the only safe way to clean it of varnish or deposits that have caused it to become more restrictive/lean.
Another option is to change fuel for that saw. It has been my experience that switching to non auto gas option will richen your mixture because aviation fuel or Coleman camp fuel ( I can get Generic Camp fuel marketed by Crown, in WalMart )does not have the trash additives that the trash auto fuel they sell us has. In the states, I can buy generic camp fuel. ( White Gas , Just like what Amaco used to sell as their main line of auto gas some moons ago ). When changing to or running on Camp fuel I find I have to lean my needles an average of 1/4 turn H & L needles because the camp fuel doesn't have all the crap additive to control the burn rate that auto gas has. All of my RC engings regardless of displacment run on Camp fuel. the P51 in the my Avatar has a 89cc Stihl 050 engine in it. That isn't my largest engine either. LOL Another welcome side effect of running good fuel ( camp Fuel ) is it automatically cleans all the carbon from your exhaust port and the engine will come alive within a few quarts of consumption. I like it and have run my saws on it at times because it smells go good.
God hates a Coward but is very tolerant of fools, so take that carb apart. I can send you a complete kit if they are scarce there.
Ken
If you had a kit you could clean your carbs HS jet without removing it or doing damage to it, by boiling the carb body in plain old WATER. First you would strip the carb of gaskets and diaphragms, and the LS needle and the Main metering needle that the fulcrum hooks into. Boiling water is the only safe way to clean it of varnish or deposits that have caused it to become more restrictive/lean.
Another option is to change fuel for that saw. It has been my experience that switching to non auto gas option will richen your mixture because aviation fuel or Coleman camp fuel ( I can get Generic Camp fuel marketed by Crown, in WalMart )does not have the trash additives that the trash auto fuel they sell us has. In the states, I can buy generic camp fuel. ( White Gas , Just like what Amaco used to sell as their main line of auto gas some moons ago ). When changing to or running on Camp fuel I find I have to lean my needles an average of 1/4 turn H & L needles because the camp fuel doesn't have all the crap additive to control the burn rate that auto gas has. All of my RC engings regardless of displacment run on Camp fuel. the P51 in the my Avatar has a 89cc Stihl 050 engine in it. That isn't my largest engine either. LOL Another welcome side effect of running good fuel ( camp Fuel ) is it automatically cleans all the carbon from your exhaust port and the engine will come alive within a few quarts of consumption. I like it and have run my saws on it at times because it smells go good.
God hates a Coward but is very tolerant of fools, so take that carb apart. I can send you a complete kit if they are scarce there.
Ken
I had suspected that as well but the carb also runs my 57 lean also. The 7-10 in question holds a tune on the sdc just great. It will need seals though no doubt. I've marked this 1 for a rebuild will do the works on it. It can show signs of a less than ideal crank seal on its side ever so slightly.
I have a keen ear and pick up these subtle signs
Screwbolts
Never to many Engines!!
One of the best running for the size engine I helped cut out of a saw and build mounts for was a pro 10-10, only one I did because they don't /aren't easy to make a firewall mount for. But it ran like a raped ape right up until my late friend burried it in the ground one day. Yes they made good engines.
I think I remember a discussion about that now. No harm in trying the hot water trick before messing with the actual jet. 'Course you'll need a kit either way. I like my cheapie USC for stubborn carbs. Paid for itself with the first carb it revived.
You're probably right but ain't no way I'm gonna go through all that just to run a dodgy carb lol.
Thanks for the offer there not scarce I guess just gotta jump on Ebay or other online store.
I've got quite a few Sdc carbs and kits so pretty much in the corner it goes. When I rebuild the zama my 800 will give back the 44 to my other 7-10 and I'll put the short needle 43 on the 7-10 in question. It's not set up for a long needle carb. That will spare another sdc for the 2-10 conversion.
Lol carbs get passed around alot between my saws
interesting use of a mac bet it did run well
