Rich Griff Posted June 22, 2021 Share Posted June 22, 2021 Can you take another picture of the spray bar to show where the fuel hole is, the hole that allows fuel into the intake ? It will be central in the barrel intake hole when in situe.. Quote Link to comment Share on other sites More sharing options...
RottenRow Posted June 22, 2021 Share Posted June 22, 2021 Andy, Looking at your photo you have the spraybar fitted the wrong way around. The needle valve should be on the side of the engine away from the exhaust (left hand side as installed in a model) and the short pipe (nipple) onto which the fuel tube pushes on to should be on the exhaust side. It’s shown that way in the photo in that article I referred to earlier. As Rich says, the spraybar and therefore the fuel nipple will turn with the throttle arm. Brian. Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted June 22, 2021 Share Posted June 22, 2021 See the carb Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted June 23, 2021 Share Posted June 23, 2021 Can you take another picture of the spray bar to show where the fuel hole is, the hole that allows fuel into the intake ? It will be central in the barrel intake hole when in situe.. Quote Link to comment Share on other sites More sharing options...
Andy J Posted June 23, 2021 Author Share Posted June 23, 2021 Spay bar hole is offset with the intake. Plus it definitely does not rotate with the barrel. Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted June 23, 2021 Share Posted June 23, 2021 Andy, your picture of the carb parts show the carb body to have some "rounded" corners. All the pictures of merco 61 's I have seen seem to have square ( rectangular section really ) carb bodies.... Is your carb correct for this engine ? The more simple carbs like the paw type, and it appears yours, the spray bar is nutted to the rotating "barrel" and becomes part of the barrel when tight, so rotates with the barrel. Does your engine have a threaded hole between the c/case exhaust ports for the exhaust flap ? Some more research needed I feel....a "community search".....team work.... There will be enough tell tail and staining marks on the carb parts, added to some common sense and trial and error, to assemble the carb and fit it to your engine for a bench run, assuming all carb parts are present, run rich for first one, straight castor..... Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted June 23, 2021 Share Posted June 23, 2021 Ah, now your last post appears, with a current picture... How many fuel holes are there in the spray bar intake area ? Maybe a washer removed from fuel nipple side would place the fuel hole more central... Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted June 23, 2021 Share Posted June 23, 2021 Here is another Merco offering Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted June 23, 2021 Share Posted June 23, 2021 7 minutes ago, Andy Joyce said: Spay bar hole is offset with the intake. Plus it definitely does not rotate with the barrel. Can you take this picture again without the woodscrew please... Main needle spring clip bent, be carefully it may break... Spray bar should rotate with the barrel... Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted June 23, 2021 Share Posted June 23, 2021 3 minutes ago, Denis Watkins said: Here is another Merco offering Yes, this is the carb type on my marine units, and probably the 35 aero....from memory I thought the "barrel spring" was conical but picture shows it to be not, the larger coil spring next to the throttle barrel. Quote Link to comment Share on other sites More sharing options...
RottenRow Posted June 23, 2021 Share Posted June 23, 2021 Andy, Your most recent photo makes things much clearer and I can see how it works now. There is a large washer with a flange around two-thirds of it’s circumference which is holding the barrel in place, and the throttle arm moves in the gap in that flange. The spraybar does hold it all together but does not turn with the barrel as you say. The older Merco carbs definitely have the rounded corners, I think this is for Mk1 to Mk3 of the 61s. I would imagine that as things wear there would be ample opportunities for slight air leaks to occur which could make it difficult to obtain a reliable tickover. The later carbs (such as Rich’s) would almost certainly have had the same diameter fitting into the crankcase and may have been used as replacements for older ones if required. Also note that the early versions of the engine had a rotating flap on the exhaust that was coupled to the throttle lever, which meant that no silencer could be fitted. I don’t think you would want to try that nowadays, just imagine the noise! Brian. Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted June 23, 2021 Share Posted June 23, 2021 Ok, so there must be a way of holding the spray bar "still", else it would rotate when adjusting the main needle ? Quote Link to comment Share on other sites More sharing options...
RottenRow Posted June 23, 2021 Share Posted June 23, 2021 Rich’s carb, and the one shown in Denis’ article, are both of the later design which has little in common with the earlier type as fitted to Andy’s engine. Their construction is completely different as is their operation, as the later carb is a twin needle type. Andy’s old type carb is an air bleed carb. I would suggest that the only similarity between the two types is the spigot diameter where they fit the engine crankcase. Brian. Quote Link to comment Share on other sites More sharing options...
Andy J Posted June 23, 2021 Author Share Posted June 23, 2021 Cant recall how well the engine ran at tick over as it was over 50 years since it was last used on a regular basis. However it ran without issue for many outings in a Super 60. Will put it on a test bench and see how it now runs. More interested to see if it now leaks any fuel from the front bearing as this was a major issue when I briefly tried it a couple of years ago. Quote Link to comment Share on other sites More sharing options...
Andy J Posted June 23, 2021 Author Share Posted June 23, 2021 5 minutes ago, Rich Griff said: Ok, so there must be a way of holding the spray bar "still", else it would rotate when adjusting the main needle ? There is a fixed nut on the fuel intake side Rich so that is held as you tighten the nut on the needle side. Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted June 23, 2021 Share Posted June 23, 2021 (edited) 15 minutes ago, Andy Joyce said: There is a fixed nut on the fuel intake side Rich so that is held as you tighten the nut on the needle side. Which suggests the spray bar rotates with the throttle barrel ? If it was designed so the spray bar does not rotate, there must be a means to stop it from rotating with the throttle barrel ? Anyways, would be good to get the engine running again...and installed in a period model plane... I am sure Andy will post feedback and some good news, a bit if "howling" merco music. New piston ring so a carefully run in period. Ic engines are fun... Edited June 23, 2021 by Rich Griff Quote Link to comment Share on other sites More sharing options...
RottenRow Posted June 23, 2021 Share Posted June 23, 2021 I have made a quick sketch of the assembly Rich. I have ignored the air bleed and throttle stop etc. In my sketch, parts A, B, C and D are all tightened together through the carb body. The barrel is trapped inside these parts but is loose enough to turn via the throttle lever, which protrudes through a slot in the flanged washer (B) which you can see in Andy’s most recent photo. Please note that the sketch is simplified and doesn’t show every part. Good luck with the test run Andy. Brian. Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted June 23, 2021 Share Posted June 23, 2021 There you go Andy, a schematic courtesy of RR, nice one RR... Quote Link to comment Share on other sites More sharing options...
Andy J Posted June 23, 2021 Author Share Posted June 23, 2021 Schematic is missing the thrust washer that goes between the barrel and item C. Quote Link to comment Share on other sites More sharing options...
Andy J Posted December 31, 2021 Author Share Posted December 31, 2021 (edited) Well its now December and have finally got round to running the engine for the first time given I acquired an engine test stand for a Christmas present. First issue, despite the engine having good compression, it does not draw fuel very well when primed. Possible that this is due to the very small bore in the fuel line as I used a SLEC 2oz tank I had lying around the workshop. Pipework that came with the tank was indeed very small internal diameter. Second issue was that the engine required a squirt of fuel in the exhaust to get it to start so not sure it is drawing fuel from the crank although it did continue to run once started. However once the glow plug is disconnected the engine stops. Fuel still leaks from the front bearing so unsure if this will improve once the caster does its job and gets burnt in. Could all of the issues above indicate that I have assembled the engine incorrectly? Edited December 31, 2021 by Andy Joyce Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted December 31, 2021 Share Posted December 31, 2021 The motor should draw fuel from a small bore piped tank on a test stand Andy. No 2 stroke tolerates a pressure drop from the leaking front bearing, making fuel draw difficult and tuning probably impossible. You cannot rely on castor or any other blockage to take up holding pressure. Motor Stopping, after glow lead removal indicates a plug way past its useful life, so change that/those. I would start with the plugs And blow down pipes around the carb, just to check they are free. Quote Link to comment Share on other sites More sharing options...
Andy J Posted December 31, 2021 Author Share Posted December 31, 2021 Motor has two plugs Denis so don't think that is the issue but I am no expert on engines. Leak on the front bearing could well be the issue but not sure how I could reduce it other than dismantling the engine again and applying some bearing seal. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted January 1, 2022 Share Posted January 1, 2022 (edited) 18 hours ago, Andy Joyce said: Motor has two plugs Denis so don't think that is the issue but I am no expert on engines. Leak on the front bearing could well be the issue but not sure how I could reduce it other than dismantling the engine again and applying some bearing seal. Hi Andy . Replace the front bearing with a sealed bearing. Remove inner seal leave outer seal in place . This will help restore crankcase compression which is more important than cylinder compression on a two stroke. It does sound like the crankshaft bore in the case is worn probably due to being run with worn bearings. This will also be the reason it doesn't draw fuel well. To overcome the leaking case you are likely having to run it very rich to compensate for fuel leaking out of front bearing. This will cause plugs to go out when bakery is disconnected. Castor will not seal any gaps or seal bearings. Anyone who told you that had either been at the fairy dust or the date was April 1st. Edited January 1, 2022 by Engine Doctor 1 Quote Link to comment Share on other sites More sharing options...
Andy J Posted January 1, 2022 Author Share Posted January 1, 2022 The front bearing was a sealed one ED, so will try using a drop of locktight when I refit it, that's if it comes out ok. Assume the case will have worn as the engine has never been serviced over the last 55years. Most of that time it has sat on a shelf although it did do a lot of flying in several Super 60's I had in the 70's. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted January 2, 2022 Share Posted January 2, 2022 Hi Andy. Sorry missed that you had fitted a sealed bearing. Bearings g fit will only seal if its leaking around the outer race. Try the crankshaft in the bare case and check play in the case behind the front race. If this is excessive you can shrink the case to a snug fit around the shaft but you will need a lathe to make the tool. If play in too bad then only real solution is fit a bush or replacement. Good luck with renovation. Quote Link to comment Share on other sites More sharing options...
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