The Mower Bench

[tomlt]

Hi Barrie,

 

I was hoping you'd reply with your wealth of knowledge on these matters. Let me answer each question in turn...

 

How are you testing compression?[/i] I used a brand new compression test gauge from screwfix, it's a max pressure type gauge screwed into the spark plug hole (as I believe most are). I simply gave it Wide-open Throttle and cranked it over for a couple of seconds before reading the max off the gauge.

 

If its running lean you will have a very light grey/white plug so thats worth a check, but if it is lean running thats the problem you should be able to smooth out the engine with the choke partly on, this could help to diagnose.

 

I checked the plug and the colour seemed fine, but I've only run it for short periods (2-3mins) through fear of cooking it. I'll check the new plug again tonight.

 

Running lean could get the engine hot, but in reality if there is fuel starvation there won't be much power so not much heat build up. Exhausts do get very hot very quickly so yours may not be over hot and you may be reading too much into it.

 

Quite possibly, but the whole engine seems to running a lot hotter than it ever has before, I'm worried about cooking it so don't want to run it for extended periods. It's giving that characteristic "realy hot" smell (if you know what I mean) and the exhaust "tinks" away after just a few seconds of running.

 

These engines are prone to head gasket failure. It usually manifests as burning oil though, and as you have had the head off you should know if the gasket was OK, I guess you did fit a new one?

 

Surprisingly the gasket was in really good condition, I was expecting to see some blow-by but no signs of it. I've got a new gasket on order, but for the purposes of diagnosis I put it back on with the same gasket (carefully) and toruqed her down per spec. Theres no signs of leakage coming out around the gasket, or any signs of oil making it into the combustion chamber past the gasket.

 

 

Carbs are not too expensive, but you need to be sure thats the trouble before fitting a new one.

Yep, I'm not sure how much more I can diagnose from the Carb, as a diesel engine guy, my knowledge on carbs is limited to pulling it to bits and giving everything a good clean with carb cleaner. There doesn't really seem to be much to these Nikki Carbs unless I'm missing something. I'll try what you suggest above with the choke and see if that makes things better when running.

 

Make sure the fuel tank is breathing OK, try it with the cap removed. Also check the fuel flow through the primary fuel hose twixt tank and filter, just in case its partially blocked. It could be that it runs OK on the first full float bowl which does not then fill fast enough to keep it running.

 

Should have mentioned I tried running with the tank cap off, have had the fuel pipe at the Carb off (loads of fuel flow) and replaced the inline filter so I think thats all good. She fires straight away so I'm not seeing fuel starvation type issues from cold or anything.

 

Might be just worth checking the timing (flywheel key) and the magneto to flywheel gap.

 

Should have mentioned I checked this also, the flywheel key is intact and flywheel in good working order. The magneto is very tight to the flywheel I'd guess a few thou at most, but it's caked in light dust and doesn't look like it's moved since I've had it. Everything's tight on it, the only issue I've noticed is a bit of a crack in the lacquer where the HT lead joins the magneto. Could you tell me what the proper magneto gap should be?

 

Many Thanks, Tom.

[adw]

Used to get similar problems on AYP mowers, turned out to be faulty micro switches, either under the seat, or the clutch pedal, there should be a single earth cut out wire from the engine, diss connect to rule out a micro switch issue, just a thought.

[GardenKit]

Tom, the magneto clearance should be 10 thou (the thickness of an average business card).

 

But I have to agree with ADW, and I thought the same last night after posting my reply, that it does sound a little like a micro switch problem. If these switches play up they rapidly make and break contact causing the ignition to cut in and out.

 

As ADW said, if you locate the earth wire from the coil to the wiring loom and disconnect it then you can rule that one out, or not, as the case may be.

Good luck

[tomlt]

Barrie and ADW huge thanks for the advice, I disconnected the coil as you said, but that didnt make a difference, set the magneto air gap and gave in/under a thorough clean to boot, gap moved from about 2thou to 10thou, but still no joy, so it was back to something Barrie suggested above.

 

With the aid of my beautiful assistant (aka the wife) I had a good play around with the choke setting, using my hand at about 6 inches from the muffler output running as it was the gases were hot (unbearably for more than a few seconds), slowly choking it up to just the point before it started coughing, the exhaust gases cooled off significantly, it ran there just like it used to for 10mins quite happily, definitely pointing to an overly lean mix. So carbs come off, had another thoroughly good soaking in carb cleaner and hey presto she seems to be back to normal (ish). Ive just mowed the 2/3acre in an hour with it and it seems to be running pretty well, although I do keep getting the odd whiff of hot engine, but that might just be alll the carb cleaner and brake cleaner burning off.

 

So im planning to strip her down now, replace head gasket, replace rocker gasket and redo the valve clearances (if needed) and give her an oil change. Im wondering if a carb service kit would be a good idea, but frankly nothing in there looked worn or perished.

 

Cheers again guys, great forum! Tom.

 

P.s. I think you might have another aspen convert here soon!

[GardenKit]

Glad we were of some help Tom.

[agg221]

Alec,If you let me have the model number and product code I will have a look on the IPL's and see if its still available.

 

Barrie

 

Thanks Barrie,

 

It's a Wheel Horse 111-5. It dates from 1986 so I fear the part is no longer available but any help or thoughts on graveyards where such things may be had are welcome. It's a double pulley which drives the deck and the gearbox.

 

It's the rim which has collapsed when the deck jammed suddenly, so no chance of recovering the existing part.

 

Alec

[mikerecike]

I'm no expert but wondered if it was drawing air in at the join of carb and engine.Can't picture that set up but easy to test by squirting a bit of wd 40 around the mating surface during running.

[GardenKit]

Does it look like item 11 on this Alec?

 

If so its part number 110361. The last price I have recorded is £45.00 plus vat. A quick search reveals it as being obsolete, but a Toro main dealer may know differently

 

Barrie

 

[GardenKit]

I'm no expert but wondered if it was drawing air in at the join of carb and engine.Can't picture that set up but easy to test by squirting a bit of wd 40 around the mating surface during running.

Wondered the same myself Mike. but discounted it as Tom had had the carb off, as well as the cylinder head to which the manifold bolts, so reckoned he had checked it out.

 

The WD 40 is a good trick, carb cleaner is even better as it will get sucked in through an air ingress leak and cause a noticeable rise in revs!

[GardenKit]

It can be frustrating, being a dealer, and having to get sense out of some customers.

 

This little story is quite typical of one we get quite often.

 

Customer " I need the main drive belt for my ride on mower"

Me "Which drive belt would that be then"

Customer " are there two then?"

Me " sometimes more, which one do you need"

Customer "not sure now, but like I said, the main one"

Me " so is it the transmission that does not work or the blades?"

Customer "uhh"

Me " does it move forward but not cut, or does it not move forward?"

Customer " not sure now, think it does not cut"

Me " so we think its the deck belt, is it the one to the deck or the one that links the blades"

Customer "are there two then?'

Me " sometimes only one, often two. What machine do you have"

Customer "don't know, think its red"

Me " I really need the Make, Model, type and serial number"

Customer " for f**s sake, you are just being awkward, just let me have a belt they are all the same"

Me " honestly, I need more information"

Customer " christ, only came to you because you are local, i will go somewhere else where I don't get asked so many questions, I only want a belt, can't be rocket science"

 

:confused1: