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Collection, Preservation and Display of Old Lawn Mowers

Latest Edition of 'Suffolk Issues'

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Hi all, again,

Yes I've discovered a new problem with my Suffolk 75cc engine, When I start it up it knocks very loudly whilst running, I've never had this problem with any of my engines so I havent a clue as to what to do. I removed the head and when I did so, some dusty looking smoke came out, this could just be the oil smoke, I inspected the bore and all around and other than the usual oil all looks fine. It knocks a bit when I turn the flywheel by hand, but I think I remember this before but I am not sure.

Ed Redfern if you are reading this ( or listening), I have cleaned the points and polished them and I have a great spark, I can even get a good one from spinning it by hand without the pull start!

Just after some advice.

 

Thanks,

Henry.

redfernmowers Mon, 17/09/2012

Hey,

was just listening to your post.. I hate to say it but the loud knocking sounds like one of two things. either the timing is out when you stripped the engine, or the piston rings are failing. without properly checking the settings of your engine, nor opening up and checking timings, I can't be 100% sure. either way though, any further running damage could kill the engine.

I have to admit I admire your drive to see this through, but once loud knocking starts and dust starts forming, there's something seriously wrong. without going through my engineering specification files, 

If I was in your direction, I'd come over, check the engine over and give it the full works. but as you've gone through a series of faults and tried to solve each one, this one wants to go over to the other side. Some machines do, others want to stay on a bit longer..

best thing if you can is find another engine like this. is this mounted to a machine at present or just a standalone engine?

take care good friend and have fun.

I'm just getting ready to take on my  other gas welding gear and some tanks so will have further gas support to hand. second hand but better than nothing. plus it's high spec gear. I know what I'm after. November will see the start of what could be a fruitful market for me. custom grass boxes and parts for restorations, etc. so all being well, let's see.

ed

HenryB Mon, 17/09/2012

I did take the points apart and then moved the whole ignition assembly because I found that the points were closing before TDC, moving this wasn't a good idea I realised so I tried to move it back to the same position. I read that engines should spark before TDC, I'm not sure though but I put it back where a mark was left around the bolts. The knocking wasn't occuring before the ignition clean. One other possibility is that I didn't tighten the flywheel nut up much in case I had to take it back off, it was firm when installed.

I will have a good look.

Henry

HenryB Mon, 17/09/2012

I did take the points apart and then moved the whole ignition assembly because I found that the points were closing before TDC, moving this wasn't a good idea I realised so I tried to move it back to the same position. I read that engines should spark before TDC, I'm not sure though but I put it back where a mark was left around the bolts. The knocking wasn't occuring before the ignition clean. One other possibility is that I didn't tighten the flywheel nut up much in case I had to take it back off, it was firm when installed.

I will have a good look.

Henry

wristpin Tue, 18/09/2012

75cc  22-24 degrees Before Top Dead Centre

98cc  23 -25 "            "         "      "       "

Use either a timing disc or a strip of paper around the flywheel to measure this. Or pick up on the old fixing marks.

Would not have thought that late sparking (retarded ignition) would cause a knock  - more likely to be caused by over advanced ignition (spark too early).

Think that you can download and print off a timing disc from various websites and then glue it to some stiff card.

 

HenryB Thu, 20/09/2012

I've got the suffolk running well-ish now, I even mowed the lawn with it! I'm not sure how long it will last but I gave it my best shot.

 

Henry.

redfernmowers Thu, 20/09/2012

Well done lad. you've done it. sorry about the doubts on it surviving. sounds like you've got it running. timing on some engines can be fiddly. that's why when I strip an engine down. if there's no marks. I set at TDC. then spot punch or pierce drill a hole at each part lined up. that way I can feel where I'm going on a timing issue.

ed

HenryB Thu, 20/09/2012

I will see how long it lasts, i was intending of doing a proper restoration but I dont think i should, the engine would let it down, if I get another suffolk engine to fit it then maybe. It has some scoring in the bore and is generally pretty knackered, apart from the magneto which produces a great spark.