Thread: Lucas woes

So now there's a market for performance exhaust systems for Lucas What reply have you received from Lucas ? I'm surprised they haven't reacted accordingly and beefed up their standard one.

Yeah, I think if it was Lucas manufacturing the engine they would have, but they use the engine as supplied from Briggs or for model 8's Kohler. Any warranty stuff with the engine has always been through Briggs. Lucas will arrange it for you, but Briggs deal with it, that's been my experience with the muffler to date.

tob job, I still have an original muffer on my 1996 6'', it's had a little rust on it for the last few years but still seems quite solid, why do you think the B&S ones were buring out ? I did wear out a gas strut a couple of years ago, I think that was becauce it sits so close to the muffler, I thought of tacking a metal heat shield on the muffler to try and prevent that overheating but still have not done it. Anyway you new muffler looks like it will sort out you're issues, that one thing I like about Lucas Mill, they can be worked on and improved, though it should be none that it was infact a B&S components made in the USA that was at fault, not Lucas.

Yeah exactly it was a B&S component which kept fraggin out, nothing really problematic as far as the machine went generally.

I too have done a gas strut and I should have kept the old one to see if I could get it re-gased, but I didn't so too bad for me

On the shield side of things for the strut, Neil did make me up this gizmo. I have painted it with flame proof paint and it will sit about half an inch off the muffler to help block a bit of radiant heat to the other things around the muffler.

way to go

What engine/size do you have on yours Johnny? had any trouble with backfiring on shut down? Have you had it fom new? if so how many hours has she done?

Sig, I don't know how much work you do with that engine but if it were my machine I would take it to someone that knows about engines, probably not your local mower shop or small engine "specialist" and get the fuel mixture checked. Burning holes in mufflers means the exhaust gasses are bloody hot and this means that, from my limited experience over about 40 years of buggering-up small engines, the exhaust valves and valve seats are going to be even hotter!
With luck I will be wrong but if I'm right you might just need the mixture adjusting and use slightly higher octane fuel which burns cooler.
When I say "knows about engines" I mean someone that has to deal with things other than lawnmowers. Almost any idiot, including myself, can set up shop as a mower and chainsaw fixer-upper if they have the money to buy the stock and pay the rent. Perhaps you can find a place with an exhaust gas analyser that can check things over for you.
Dennis.

its the 15 or 16 hp B&S Vanguard, I have not had it from new, it is a early model , therefore hasn't an hour meter. It has done quite a lot of hardwood milling, mainly 6" cuts. I do recall a bit of back fireing once or twice. It can be the ignition coming loose or even a bit of water in the fuel bowl, doubt that you would have that problem. you're engine could be a bit out of tune, if the valves are not adjusted correctly, you could be geting combustion out of the exhaust valve and into the muffler, Fairly easy to adjust if that is occuring. I think I was able to specifications off B&S website.

My 2 bobs worth

Backfiring. burning holes in mufflers, running on - to an experienced person sounds more like it would be related to ignition timing, spark plug heat range, carbon in cylinders, or even the type of fuel you run. When this motor was designed it probably ran on super petrol or standard which had a lot more "oil/lead" in the fuel (wasn't as dry a burner) as the current unleaded petrol. Try adding some additive that you would for say an old eh holden or something like that and maybe the timing might need to be advanced or retarded to cope with the hotter burning fuel.

You should be able to google something on leaded/unleaded fuel comparison/changover.

added - just had a quick google and the lead increased the octane range so try useing the higher octane fuel and as it doesnt lubricate the valve seats as well they can get small pits in them which would "glow" resulting in running on and afterburn/preingnition(backfiring/pinging). I would suggest trying an additive as well. They used to recomend retarding the timing but if you are runnign on high load for long periods then that may actually make it run hotter, so i would try the higher octane (dearer) fuel with an additive and see what the result is. Continuing as is you could actually end up melting a piston which is more exky than a couple of cents per litre for petrol.

Cheers

i agree too much combustion heat sounds like that motors running lean

She only used to back fire on shut down, now I just idle it right down and let it idel for 10-20 secs then switch off - no backfire.

The exhaust has been an issue and yeah it gets really hot, this new one is set to fix that and also reaming out the main jet on the carby a couple thou should cool her down a lot.

At times some people have said I should be using premium unleaded, but as many people have said it won't make a difference - who bloody knows? not me!

I don't have any issues with running on, don't recall mentioning it either???

I dont necasarily think it is running lean - i think hotter is the problem.

When you are milling it is running at full (or almost full) throttle and under load for lengthy periods so the heat is building up. If you are not idling much you could also look at running colder range spark plugs. Try the high octane fuel and see if it makes a difference - you wont notice the power but you may notice the heat is not as big a problem. If there is any way to check the timing it may be able to be advanced slightly to also help run cooler.

More fuel may not overcome this problem, in fact i think spark/lubrication is more the area to look at. - does it blow any smoke? - what colour? When you remove the spark plug what colour is it? Does it have any "dags" hanging on it??

I didnt say you mentioned running on or pinging but that can be one of the symptoms of a "hot" motor.

Cheers

a motor 2 or 4 stroke if running lean will increase combustion temp

Originally Posted by tlbsg

a motor 2 or 4 stroke if running lean will increase combustion temp

Yes but if it is not running lean then more fuel will not cool it down, it will only go out the exhaust as smoke and end up as unburnt gas that can ignite when you shut the motor off - called backfire -

There is nothing to suggest this motor is running lean - it is running hot - this is evident buy the melting exhaust and backfiring on shutdown. When it backfires what is igniting if not unburnt gas??