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Physical Size Commonality

#1

B

bartles

Sorry to ask such a potentially broad ranging question but here goes:

When comparing horsepower ranges from 14-17.5 in many riding mower brands are these different engine ratings from a common block size?

My reason for asking is I do second life rebuilds on 38-42" mowers. I have a good 17.5 hp model 31R 977 0001 G1 and was wondering if it will fit the mounting bolt hole arrangements and crank size and lengths for other single cylinder ratings.

Thanks!


#2

StarTech

StarTech

Most time those Briggs in this size range will have the same mounting pattern. As for crankshafts that is one that has to research as there are several several sizes used. Engine horse power rating are all over the place. Some these even use restrictor plates to limit hp.


#3

B

bertsmobile1

The mounting holes are the same size regardless of engine size for OHV engines
The small increments in Hp ratings are done by choking down the carbs with restrictor plates .
So you have 5 Hp ratings for 31 series engines that all have the same bore stroke & compression rating .
Some have different governor springs as well .
The SV's generally had different main jets & governor springs .
Crank sizes are 7/8 for push mowers 1" for domestic & 1.125 " for commercials .
A rule that is honoured in it's breaking
Most cranks are the same length.
However as the strokes get longer the crank cases get bigger so you can run into clearance problems between the mower & the dash tower.
SV's sit higher off the floor than OHV engines do .
Found that one out when trying to fit a OHV into a SV frame only to find it was lower so fouled the steering mechanism .


#4

B

bartles

StarTech said:
Most time those Briggs in this size range will have the same mounting pattern. As for crankshafts that is one that has to research as there are several several sizes used. Engine horse power rating are all over the place. Some these even use restrictor plates to limit hp.
Click to expand...
Hey, thanks a bunch!


#5

B

bartles

bertsmobile1 said:
The mounting holes are the same size regardless of engine size for OHV engines
The small increments in Hp ratings are done by choking down the carbs with restrictor plates .
So you have 5 Hp ratings for 31 series engines that all have the same bore stroke & compression rating .
Some have different governor springs as well .
The SV's generally had different main jets & governor springs .
Crank sizes are 7/8 for push mowers 1" for domestic & 1.125 " for commercials .
A rule that is honoured in it's breaking
Most cranks are the same length.
However as the strokes get longer the crank cases get bigger so you can run into clearance problems between the mower & the dash tower.
SV's sit higher off the floor than OHV engines do .
Found that one out when trying to fit a OHV into a SV frame only to find it was lower so fouled the steering mechanism .
Click to expand...
Thank you!


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