OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Briggs Quantum Stalling

Well, I used it yesterday and was not overly impressed. I needed to give the lawn a slight scalp (They suggested de thatch on Gardening Australia Friday). I didn't take a photo, but it wasn't anywhere a severe one. Plus, I mowed last week, so I am quite sure I wouldn't shock it.

Put on some bentonite clay after mow to hopefully help the sandy soil, and a very light natural fertilize before the thunderstorm we are scheduled for tomorrow (hopefully pelt the clay in further than the sprinkler).

Back to the mower, started first go and mowed the back lawn without any major issues. Got several catchers off.

Then the front - a fair bit harder cut. Full throttle, slow push, stall. Repeat, same. Check full RPM - 3190. Upped it to 3300 - no difference. Ended up cutting 13-20cm strips so it wouldn't die.

The way I see it now (after stalling a Quantum 50 about 8 times in conditions a PT wouldn't have batted an eyelid over) is they are the mower equivalent of a Commodore 4 (the one with the Starfire).
They get along mostly fine in normal use, but its when you need power, you suddenly realize its not there.

It is not a fault in the mower - its just how it is. The thin quick cut blade bar wouldn't have helped its power.

Anyway, I persevered and got it done (couldn't be stuffed getting a PT out with not all that much to go)

To its credit, it worked very hard. I gave it a unloaded run at 2500 for 2 minutes part way through to cool it down. There a slight weep in one of the gaskets which occurred after the last oil change (must have cleaned crap out) so it used a bit of oil, and for the first time I noticed a little oil smoke when it revs up (practically nothing). At the end, it used from full, down to a bit over half way between full and add on the dipstick. Will add some rislone stop leak to the new oil (changed it after the mow - still relatively clean)

Whether it's because of clearances from its chinese manufacture, I don't know. It had semi synth 15w40 in the sump, so maybe a bit of burn when really hot.

Plug burn was perfect - little bit of oil residue

Love the snorkel - was dust flying everywhere - and when finished, the new filter and pre filter was near spotless.

G'day Tyler,

3200-3300 rpm at full throttle is normal for one of these - I have a May 2001 built XTS50 [think it's US origin], on an alloy chassis Masport Maxicatch 550. With the snorkel, too - a very good idea, that.

This one has the Quickcut cutter bar too, and it seems to work pretty well. It does have problems ejecting the clippings in really heavy growth, but doesn't seem to lack grunt, at all. So in these conditions, I just do a first cut at max height setting [or run the line trimmer over it], then a second cut.

With these older-design sidevalve Briggs, they were designed to use SAE30 monograde mineral oil. I have zero oil consumption issues, running Penrite Small Engine SAE30.

From experience, even using a 20W-50 multigrade oil in one of these sidewhackers will result in some oil burn.

Hi Gadge

I had an inkling 3300 was the top - any more than that I though was pushing it. I agree, the main issue is clearing clippings - I actually went up 2 levels at one point with a bit of improvement and then went back over.

Probably more an indication of reciprocating mass than a poor engine I suppose - the little gxv120 on the big bob is 70cc less and will go through much thicker grass (though being a side shooter it is under much less load)

I sometimes run sae30, but I an never get it at a good price - always pushing $30 for 5L. I bought a tonne of Castrol UltraClean 15w40 at autobarn for $12/5L bottle.

I use very short oil change intervals (often change after every mow until I am happy its staying clean) so at $1.40 ish per oil change with the 15w40 semi, it is quite economical. Before I put this oil in, I use the cheapest 15w40 I can find (usually Nulon or gulf western mineral) to flush the muck out for 2 or 3 changes.

In normal use, I notice no consumption. Briggs recommend 10w30 up to 37 degrees - but I reckon thats a bit too thin (can only imaging how much I would have burnt on saturday.
Apparently, 15w40 is the most shear stable multigrade.

Its only in this heavy cutting I have noticed oil consumption. Still, I believe it leaked a fair bit of this.

That being said, a friend never checks his oil so I use sae30 in his.

G'day Tyler,

Agreed, that it's not easy to find SAE30 at a discount - Autobarn sometimes has weekend 'storewide x% off' sales, and I picked up a 5L of the Penrite SAE30 for somewhere in the $20s there, a while back. Lasts me a long time, as I only have two 4-stroke mowers.
They haven't had it for a while, but Autobarn also used to have specials on Valvoline 20W-50 mineral @ $12/5L or less.

My Big Bob is currently waiting on reassembly, after a partial teardown to install some chassis bits from a donor machine. Like you, that machine is my go-to for heavy growth - the 4hp Briggs chugs on through it. Fitting the extra pair of blades seemed to help with that, too.

Hi Gadge

If you only have a few 4 strokes, 30w is definitely the way to go.

Unfortunately, I can't pass up free good condition 4 strokes, so have amassed a fair few. I can see why people go for them - quieter, no fuel mixing, enough power for most. But, they just can't compare in the thick stuff

If I had a lot of time on saturday I would have done a comparison - 2 blade PT V SPFC 160 V 4 Blade Chonda on Honda deck V Masport quickcut with xts50 V Masport quickcut with Quantum 35

I reckon they would finish in that order (best to worst)

Have got 5L of Valvoline 20w50 from a few months ago's special - $9.99. It was ear marked for the Camira, however I grabbed 2x GTX 20w50 last month - again, Autobarn $9.99. Lucky if it does 500km between oil changes though

Last time I used Big Bob, he only had 2 flat blades, but have a pair of low lift blades ready to add for next use. Have to wait for the verge to grow haha. Did your Big bob handles shear?

G'day Tyler,Don't know that fluted 'lift/fan' blades would offer any advantage, on a Big Bob. I just fitted a second set of the OEM type flat blades.

Yeah, the handle bracket fractured, for the second time - on the near side in this pic:



And a FleaBay donor mower @$20, which had the '3rd gen' strut reinforced bracket type, was by far the cheapest repair option.

Just a quick follow up on this, I bit the bullet and purchased one of these masport quadcut discs (plus stiffener ring)

https://www.gaspares.com.au/products/BLH7932?

I put 2 blades to try it out, 2 minute install with the rattle gun. Reconnect plug lead, check oil, new fuel, turn on fuel tap (added that a while back), 4 primes and went with a quarter of a pull. Then settled down so much smoother than before. Quantums are generally quite good, but the big blade disc just completes it

For under $40, its a completely different mower.

I plowed it through a small bit of grass 65-70% as thick as what was absolutely killing it before - now at only 1/2 throttle without any significant bogging. Threw grass to the back of the catcher and packed it much better. Significantly less muck build up on the deck (to be expected).

Ended up putting the top end back to just on 3k rpm - just because it doesn't need the top end anymore but is nicer to have slower idle

Now I just need to work out the old Masport 400 - turns out someone mig welded a victa boss onto the quickcut masport bar. Will probably just throw a Rover disc and boss on that one.

Will eventually convert the other couple of masports I have

Actually, scratch that, I seem to remember the rover being about 5-10mm bigger, so that won't work, just in case anyone tries this in the future

Hi Tyler,
I don't sell a mower anymore with a blade bar on it, the idea is just cheap junk. Sometimes it takes hours to set one up with a proper blade carrier but in the end it is worth it, smooths them out and makes them feel much more solid
Having said that I have had 3 of these small mowers (sprinter type bodies) come back recently with blade problems and no idea why. First one was a Sprinter with a Briggs and I had fitted a Rover blade carrier and the 3 screws holding the base had come out, never had that happen before. Second one is baffling the 2 blades had completely vanished to the point I was thinking did I fit blades to it. The bolts were tight and there was no sign of any bit of blade under the bolt head, both blades missing, defies logic. I know it had blades because she had cut the lawn several times. Third one was a Sanli I had put a Briggs on and used the Sanli blade carrier on it and the blades had become very loose for some reason but the bolts were tight and it hadn't done much work. 3 mysteries I don't have answers for.

Hi Norm

I would never sell a mower with a bar blade on it either - too many issues hitting things. These quickcut swingback bar systems are a step up from that, but still lousy.

When you say the 3 screws holding the base, do you mean the 3 small blade boss screws? If so, I have personally had that happen to me 2x and seen it another 2.

Perplexing how blades could disappear without a trace. Only thing I can think of is poorly heat treated blades, or the 'grain' flowing across the blade - so it practically sheared at the highest stress point; the bolt.

Hi Tyler,
yes it was the 3 small blade boss screws
As for the missing blades, I can see no way they could disappear and leave no trace of them ever being there. I had to ask the woman if she had actually cut the lawn and she said she had and it worked fine