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Post by onlyhomelites on Sept 5, 2020 8:43:56 GMT -5
I've had a couple customers from Canada ask me about parts and/or the purpose of the valve and extra fuel hoses on some Terry 330's. I had no idea, as the one Terry IPL lists the parts but does not show them on the diagrams, so I never got any deeper into the mystery. But yesterday I finally tore down a parts saw I bought from Canada almost a year ago and wouldn't you know, it had that system!
So through disassembly, guessing and some logic applied (dangerous, I know!), I finally figured out what the purpose was...just like the title says, it was an adjustable fuel heating system. The main fuel hose tees just out of the tank and goes over to a simple screw valve in the back of the carburetor chamber area. Then the hose goes all the way over to the engine block, near the coil and they formed a "heat chamber on the side of the cylinder. There is a hose barb top & bottom and a cover plate with a rubber gasket & 4 screws. The fuel dumps in there, heats up on the side of the engine and then goes out another hose that goes under the engine and comes up the clutch side and back to the the carburetor. The Zama H7 carb has a second fuel inlet barb near the first for the heated fuel to enter and then mix with the unheated fuel before it hits the fuel strainer screen. The video is a bit long, but I wanted to document as much as possible and I didn't know what the hell I was doing!
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Post by timinnb on Sept 5, 2020 12:52:07 GMT -5
Only in Canada eh!
Leon, I had originally thought that maybe all Canadian 330's had the winter kit but my 330SL does not have it, only my 330HG (UT no. 50198, ser no. T83 00215). When I was looking for the two fuel lines 93157-30 & 93157-43, they were for the heater lines. My saw has a C1S Zama H-7-25C. I purchased the two "valve - check" part number 96217 from you, which is the removable piece you turn with the screwdriver. Too bad someone didn't have a Canadian 330 owners manual that might show how you were suppose to operate the heater. Thanks for the video!
Tim
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Post by onlyhomelites on Sept 5, 2020 19:53:32 GMT -5
Yeah, I'd love to see some literature on this. I'm assuming when it's above freezing, you close the screw entirely...but that's only an assumption!
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Post by rowdy235 on Sept 6, 2020 6:36:30 GMT -5
Very interesting. I wonder if vapor lock would be a problem if you forgot to adjust the screw in warm weather. Maybe not with the design of the system. Vapor lock used to drive me nuts on my old grand wagoneer. On a side note, at what temperature does gasoline begin to get affected by cold? I know diesel gels pretty easily but have never seen that issue with gasoline. Now, getting one started when it’s cold can be another story. Safe to say I wouldn’t want to be out cutting if it was cold enough to gel gas  Either way, very cool piece. |
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Post by edju1958 on Sept 6, 2020 9:42:24 GMT -5
Rowdy,I believe gasoline gels at -50F.Whoever would be out cutting wood at that temperature would need to have their head examined,Lol.It was always my assumption that we all have our wood cut & stacked way before the snow starts to fly,especially in the area where I live where we can get several feet in one snowfall.This makes it very difficult to get to a woodlot to cut.Furthermore,we're not supposed to burn green wood because of the creosote build up it'll cause.Not only the creosote problem,but did you ever try to start a fire with green wood?Also,I think the cold weather fuel heater was most likely an option that was available at an extra cost. McCulloch had a much simpler version of a fuel heater.The air filter cover had something that resembled a snorkel that you turned downward to capture the exhaust & forced it upwards into the air box to warm the fuel & carb. I suppose just about all saw mfgrs.had their own version of cold weather fuel warmers.
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Post by Clasec on Sept 6, 2020 12:05:55 GMT -5
Very interesting. I wonder if vapor lock would be a problem if you forgot to adjust the screw in warm weather. Maybe not with the design of the system. Vapor lock used to drive me nuts on my old grand wagoneer. On a side note, at what temperature does gasoline begin to get affected by cold? I know diesel gels pretty easily but have never seen that issue with gasoline. Now, getting one started when it’s cold can be another story. Safe to say I wouldn’t want to be out cutting if it was cold enough to gel gas Either way, very cool piece. I believe the fuel heater was used to prevent ice buildup in the carburetor venturi. When we rode our 2 cycle dirt bikes at cold temperatures we had icing problems. |
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Post by rowdy235 on Sept 6, 2020 18:37:50 GMT -5
I have had carb icing issues on several old Toyota’s. Those use a vacuum switch to pull air from around the exhaust manifold when cold and then switch to pulling cold air after the engine warms up. Trouble is the systems either fail or get removed over time and you end up with icing.
Guess I never thought about heating the fuel. Much easier than heating the air on this application id say.
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Post by onlyhomelites on Sept 6, 2020 20:43:53 GMT -5
The whole system is quite ingenious (I think)...I'm just not sure that the 330 saw duty in the professional setting. Like Ed pointed out, most homeowners have their wood cut long before it's cold enough to ice a carburetor. Whatever, it's kinda neat to be able to document it.
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Post by lesorubcheek on Sept 7, 2020 14:04:03 GMT -5
McCulloch had a much simpler version of a fuel heater.The air filter cover had something that resembled a snorkel that you turned downward to capture the exhaust & forced it upwards into the air box to warm the fuel & carb. I suppose just about all saw mfgrs.had their own version of cold weather fuel warmers.
The C series had an optional heat exchanger that worked similar, directing hot air from around the muffler up to the air box. Part number 59279. Heck, I think even the 410 had some setup to direct warmer air for cold winter use. Kinda makes ya think why this was an option for some saws but not all of 'em. Dan |
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Post by onlyhomelites on Sept 7, 2020 20:54:08 GMT -5
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Post by Clasec on Sept 7, 2020 21:29:29 GMT -5
McCulloch had a much simpler version of a fuel heater.The air filter cover had something that resembled a snorkel that you turned downward to capture the exhaust & forced it upwards into the air box to warm the fuel & carb. I suppose just about all saw mfgrs.had their own version of cold weather fuel warmers.
The C series had an optional heat exchanger that worked similar, directing hot air from around the muffler up to the air box. Part number 59279. Heck, I think even the 410 had some setup to direct warmer air for cold winter use. Kinda makes ya think why this was an option for some saws but not all of 'em. Dan I think this is one for a C series.  c-series heat exchanger by Clasec, on Flickr  C series heat exchanger rear by Clasec, on Flickr |
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Post by blythkd on Sept 8, 2020 6:53:48 GMT -5
All this is rather interesting. Of course I've heard of winter units, probably mostly from seeing reference to the special parts in the IPL's over the years, but I've never worked on one. I've ran standard saws to temps around zero, probably even a little below, with no troubles. Anyone have any idea what outdoor temps the winter units were intended for?
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Post by sweepleader on Sept 9, 2020 7:15:10 GMT -5
I would vote for the system having been designed to prevent carb icing. On the west coast it is possible I am sure to get carb icing at moderate temps when humid air comes in from the ocean. In aircraft I know it is possible to get carb ice at above freezing temps if the humidity is right for it.
I believe small aircraft with piston engines always take off with carb heat on to prevent icing at that critical time of the flight. If the humid ocean air was combined with freezing temps, carb icing might be quite normal.
I would bet that would be common on the west side of the Rockies. Leon, you NEED that on all your saws!!
(I am not a pilot but I read about them on the interweb.)
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Post by rowdy235 on Sept 10, 2020 15:33:53 GMT -5
I had carb icing issues on an old Toyota pickup I had once. The icing was usually the worst between 30 and 40 degrees, because there was still the potential for a lot of moisture in the air. When it gets well below freezing there is not as much moisture in the air. In that case, the trucks previous owner had removed the hot air intake which would normally allow the engine to draw air from over the exhaust when it was cold. All I had to do was pull over and shut off for a minute and it was good to go, after restarting it wouldn’t usually act up again. Something that wouldn’t be possible in an airplane |
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