I ran out of my usual "Formula 1" 20w-50 mineral oil which I needed for my annual oil change. So I decided to use Shell Helix Ultra 5w-40.

All I can say is wow! I can feel the difference, honestly! I can start the engine just by pulling the cord with my little finger, and even when cold the engine whizzes instantly up to the rev limiter. Whereas before I needed to tug the starter cord a fair bit harder and when the engine fired up, it would hunt about a little before settling. Engine seems a little quieter and smoother too.

I'm impressed - didn't think a thinner oil would make that much difference

 

Will you be moving your Flymo onto a bi-yearly service schedule now?

 

I wouldnt advise hiting the limiter when your engines cold

 

Will a thinner oil give you the protection you need, though?

 

Well now that you've completed your engine mods, is it time to move onto the suspension setup, and reduce the ride height...?

 

Don't you mean cutting height?

JohnD

 

Shouldn't this be in the muppets section????

 

What off of 2 years ago...?

 

Less bova with an hover!

 

Did you prefill the filter?

 

and disconnect the crank sensor?

 

In all seriousness (sp) now are you supposed to pre fill the oil filter when changing it? I've heard a few people saying this at work but i thought he was taking the pee. Now i'm unsure.

 

My engine doesn't even have an oil filter

 

Yea pre fill the filter, it wont hurt.

 

My mowers on the same stuff

 

Would you recommend a remap for that type of mod then

 

It will run a carburetor and ignition is probably on points so it may not have an ECU so mapping as we know it is out.
Is it 4 stroke and if so what cam are you running?
Don't waste money on V-Power as it will probably run on 91 RON OK but think about 95 RON if you skim the head so you do not run into problems with DET.

 

This is incorrect.

I have some specialist sotware i have developed myself for just this application.

ZX spectrum and Commodore 64 compatabile.

 

I'm going to lower it this weekend

 

A little head porting wont go amiss, along with the inlet tract. Thatll go nicely with a 285 degree camshaft. Wrapping the manifold may be an overkill though...

The downside will be that the b*stard thing now hovers 8" off the ground!

 

As your current setup is NA, have you considered a possible turbo conversion?

YouTube - Turbo Murray Lawnmower

Or maybe even something a little more "radical" ?

YouTube - Jet Lawnmower - Fireworks Steve
If you do go for the jet engine option, so you be careful of erm.. Catastrophic failure....
YouTube - Jet Lawnmower - Up in FLAMES!! Fireworks Steve Gets BBQ'd

 

Mowzilla Nitros mower its the future

YouTube - MowZilla Nitrous Powered Lawn Mower

Some very odd people around

 

There are bigger gains on the exhaust side so port that first. I have DEI heat wrap here if you need it to keep temperatures down.
Hovering at 8" is not much use for the purpose for which it is intended but you could drill holes in the top cover surface just a few at a time until you get the ride height. If you go too far these can be blanked off with bungs and araldyte.
What is your rev limiter set at? You could always reduce the revs a bit but remember that will also reduce the torque.

 

According to the ID plate, it was set at 2700rpm (To conform to EU noise/emission regs ), but when the spring fell off I just set it by ear, I guess its about 3500rpm now.

I could pusher it higher, but I think I need to get the blades balanced first. Biggest problem is adjusting the fueling to to cope; it s a modern carburettor thats non-adjustable (for emissions regs). I could just drill out the jet though. Or maybe fit a different carb...will a SU HIF44 fit?

I've been thinking of upping the compression ratio; Its a side valve engine, so all I need to do is skim the cylinder head. I need get some det cans or a knock link first though to make sure it doesn't det

 

Check the owners manual to see if you have the low compression 91 RON model or the high compression 95 RON GT version. If you skim the head then go up a grade of fuel eg 91 to 95 or 95 to V-Power. Of course you could run NF at 2 mls/litre.
You might want one grade colder plug.
Don't bother with a K.L. because you will get false indications when you have stone srrikes. Det cans have to be the way to go.
In view of concerns about global warming I think you should do the right thing and DEI heat wrap the exhaust system.
I can't help you on the carb front other than drilling out the main jet but it only takes a marginal diameter increase to greatly add to fuelling. Only carbs I have any recent experience on are the four on my bike and just one of these will be too big for your side valve application.
We have a lot of grass out the back you can practice on if you wish.

 

I just checked the manual and it says I should be using SAE30 it even mentions SAE10 for winter use!!!! :freak:

http://www.tecumsehpower.com/Custome...81-1215-14.pdf

So maybe even 5w-40 is too thick!

Thing is, its an American engine, and it says to use regular gasoline. But USA regular is different to UK normal unleaded, which I think is equivelent to their premium gasoline???

Maybe I should use Vpower, just in case. It also says I can use E10 fuel, so Tesco 99Ron should be ok too

 

After all that will he need traction control, i.e. lead filled divers boots.....

LOL

DunxC

 

Now speaking of bikes..... If youre going to all this trouble with the head, inlet tract and exhaust, then the last restriction is going to be the carburettor. How about some GSXR throttle bodies (or rather one)? The skys the limit: literally if you let go of the f*cker!

 

Let's not lose sight of the objective here. Around here grass does not grow during the Winter so I think that is irrelevant. I would recommend 05w-30 for your application but Oilman might disagree. There may be marginal improvements in fuel economy or blades of grass per rpm if that is how you measure it on lawnmowers, there should be a few % more bhp and you will have added protection at higher revs.
Now as regards fuel grade, I would guess it is designed to run on 91 Ron which I think is the basic US fuel grade so running 95 without NF should be good and if you have any doubts just add 1ml per litre NF to be on the safe side. No need to go to V-Power.
Does the handbook give the compression ratio?