OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Victa Two Stroke Engines Engine swap - B&S to Victa

Has anyone done an engine swap from B&S to Victa PowerTorque?

I have a spare 22" MTD sidecast mulcher chassis (bent crankshaft on the 45 series B&S). I am thinking of maybe dropping a rebuilt PT motor on it.
They are both supposed to be a standard bolt pattern - I may need to cut a slot for the muffler.
Then there's the blade mounting - MTD has a (I think) pressed on boss and a small plate that bolts into the end of the crankshaft.

It's that or a new Quantum 5.0 for $295.00 - the 3.75 just doesn't have the oomph to maintain enough blade speed when the going gets tough

Any thoughts?

I am pretty sure you will run into issues with the crankshaft being too short and also the blade boss, if it were an 18 inch cut and the crank was longenough you could probably get away with a victa blade disc.

Since you have a 22" mower I do not see this being feasable.

I put a Quantum 5hp I/C on my mtd 22" - its now a proper mower, doesn't like heavy grass 'though, really hard to push; have thought about modifying the front of the chassis but I rarely use non-self propelled mowers

Having a few shaft length issues myself here at the moment.
and the damn blade bosses.


Victas have a 40mm shaft.

MTD and Rover use a 70mm shaft.

Ive also got some motors here that have a 50mm shaft. Came off a morrison, i think old masports used these. Ive an old Rover utility toecutter thing here that looks like the 50mm would be the go on it. Not sure if this is used on newer stuff, its all older crap that ive got here.


Easy to go the other way as you can space the motor up like victa did with the forward facing silver coloured 375 sprints.



Is the 45 series a 7/8 crank??? Putting a motor on it with a 1" crank might help with the bending in future.


bob.

Thanks guys....
Joe - That's the problem (shaft length) that I have encountered. I could get an extension made, but it would be one more thing to go wrong (and not real cheap, either!)

Redeye - That sounds like the go. I've got a 2-stroke for the real heavy stuff, but it's not a mulcher - catchers are a PITA!

Bob - I'm assuming the standard shaft length is 70mm - B&S do a special "short shaft" for the Victa chassis. The 45 series is a 7/8" crank. The bending was due to the operator (not me, honest!) running into a steel peg.

So, now I order a 5hp Quantum (or for just $30 more I can get a new 6hp one - decisions, decisions!!)

Thanks again for your input, guys.

Igor, B&S seem to show the two shaft lengths in their catalogues for most of their engines, I don't think the short shaft is a specific Victa thing. Obviously the shorter shaft makes it a lot harder to bend the crankshaft.

Well id say it would not make a hell of a lot of difference if you had a crank boss adapter to get the blade disc/bar down to where a long shaft would be, its still leverage. Somethings gotta give.



I think there was actually 3 different lengths.
I just measure from the face of the casing, the correct measurements are from the mounting flange.
Something like,
1 7/8ths for victa
2.5" for masports some old rovers and morrisons.
3" for most everything else.

The other way round you can space the motor up.
Victa even did that with some of the forward facing silver sprint motors.


Tough call on the new motor.
If it were me, i would just go find a sub $40 Victa, fix it and use it till it dies. Catchers arent that bad.


Bob.

I don't like crankshaft extensions, as I have mentioned in another thread about a rideon. They are crankshaft benders.

I've only seen two shaft lengths on most of the B&S engines, but that is measuring from the mounting face - the distance they stick out from the bottom oil seal just tells you the shape of the oil sump, it doesn't say much about the crankshaft.

I've seen B&S motors on Fleabay listed as "short shaft - Victa only".

Well - the 5hp (625 Series) arrived yesterday. Bolted straight in - no safety bail (w00t!) and had to add a generic throttle control. At about half throttle, it mulched the nature strip with ease. Does feel a tad heavier to push, but I can live with that.

Bob - an acre of 4-week growth kikuyu will cure you of a liking for catchers real quick - I do half a dozen of them every week I already have one $45 18" Victa Pace I use for rough stuff, and a $120 19" Charger with 4 blades that does a brilliant finish (and works well in the wet, too!). Both have catchers - some clients are a bit backwards that way, but hey .. their money is still good

igor, if you had the speed control set halfway it should have been running at about 2,400 rpm, compared with 3,000 rpm maximum, and it will have opened its throttle wide whenever necessary. The control only changes the speed, not the maximum throttle setting. If it will do a good job at 2,400 that is excellent - I think that is about the speed most of us use when we can, and only go higher when we need the higher maximum power it can develop at maximum speed. I always feel as if the mower will last longer when I don't rev it hard.

Not so sure about mowing without a catcher. I used to do it long ago but found the cut grass formed into clumps, and soon afterward the lawn seemed to be in clumps too - it didn't grow under the clumps of grass, and they settled down and locked themselves in. It might be different in Queensland, you get the rain at a different time of year.

[quote=grumpy
I've only seen two shaft lengths on most of the B&S engines, but that is measuring from the mounting face - the distance they stick out from the bottom oil seal just tells you the shape of the oil sump, it doesn't say much about the crankshaft. [/quote]


Hmmm perhaps i need to pay more attention.

Update after a bit of usage:

The extra HP is just what this mower needed. Runs mostly on half throttle (let the governor do it's thing), unless in really heavy going. This motor does not die in the bum like the other little one did - it has enough torque to maintain the blade speed whilst the governor kicks in.

One of the biggest complaints of the "non-mulching" brigade is the lines of noticeable cut grass left by the mulch mower in heavy going. Keeping the blade speed up is the key to minimising, or even eliminating this problem.
The only other issue seems to be a design one - my son-in-laws' Victa Tornado (same motor, but different cutter setup - "turbo" disc and four blades)seems to make much easier work of heavy stuff than the bar blade on the MTD.

Removing the mulch plug and using it as a 22" utility mower is a complete revelation with this motor. I can now go through 4-week growth kikuyu at a fast walk, where before, it was ... push ...wait for revs to come back up, push ... wait .. etc. Saves much more in time than the little bit of extra fuel it uses

igor, the area you are mowing per yard of forward travel is 22% greater with the 22" mower compared with an 18", and an 18" mower with 3 hp is barely adequate - and not even that for heavy grass. On top of that you normally overlap a couple of inches between cuts, so you are really comparing 20" cut with 16" cut, not 22" with 18", so you are cutting 25% more grass, not 22% more. That means the 22" mower would be slightly underpowered with 3.75 hp, and you'd be running it at maximum speed a lot of the time. If I were buying a 22" rotary mower, I'd expect to see 4.5 hp for a normal back yard, and 5 hp if the going was likely to be tough fairly frequently. That way you could run it at a sensible engine speed instead of flat out, even in six inch grass. When you get into the 18" high kikuyu, you'll still have it flat out, and won't be walking all that fast I think. (Those figures are based on what I've found with various mowers in my back yard - my 3.5 hp 18" Victa requires maximum engine speed if the grass is 6" tall, and I have to walk quite slowly. If it's more than 6" tall, I have to go back and forth two feet at a time.)

Im hearin ya there Grumpy.

But thats why they call them Lawn mowers, not grass cutters.
3 hp will take an inch off the top as fast as you can push it. well maybe not in real thick stuff.

Saw a guy mowing with a 6hp 18" masport the other day when i picked some mowers up. He needed every HP. Instead of stopping every 3 feet and emptying the full catcher he pushed the thing around and around with grass spraying out from underneath and made a big mess and then emptied the catcher.
And the crazy asians next door to him were out mowing with the electic Ozito that was missing a back wheel.

I tied my mowers on shaking my head and headed off for home. Some people dont deserve mowers.

Oh and i had a measure, theres definately 3 lengths. 47mm 62mm and 81mm