HELP! De-restrict B&S 420cc 1650 to 2100 spec? Anyone familiar with this?

[wcorey]

Picked up a deal on a very clean Simplicity 1728 that's powered by the 420cc '1650' Briggs, which I've read is more or less the same as the '2100' as used in the 2128 model but the output is restricted somehow (1650/2100 refers to the 16.5/21.0 torque ratings). I saw reference to this on a snowblower forum but no details as to what it entails to 'de-restrict' it and a couple posters asked for more info only to be met with no response. Trade secret I guess or maybe you have to be 'in with the in crowd'...?

I've searched pretty extensively and can find no other info on the subject. Found through IPL's that they have different flywheels (so different timing?) but most other significant parts like P&C, carb, cam, ign coil, muffler etc are the same.
Could be a lot of ways it could've been done but since it was specifically referred to as as being 'restricted' makes me think of something relatively simple like choking down intake components and/or ign timing...
All else fails I'll likely try a bit of ign advance.

Anyone?

 

[huskihl]

once site says the 16.50 is 328 cc, another lists it at 420. Not certain if it’s a difference in the era or just a typo. Worth checking yours to make certain. Could be as simple as having a small gasket used as a restrictor for the carburetor. Could also have a smaller carburetor and valves

 

[wcorey]

The older ones are 328cc (or 342?) and the newer is 420cc, mine is for sure 420. I've poured over IPL's and can't seem to find the 'missing link', other than the flywheel. Head, crank, gaskets, piston, valves, cam, carb, jets, muffler, coil, all the same part #'s.
Would that much difference in torque be just from ign timing? I think they both run at the same rpm, the driveline stuff on the blowers is all the same...



25D137-0116-F1 1650 model

PartsTree - Home of OEM Parts for Outdoor Power Equipment

Parts lookup and repair parts diagrams for outdoor equipment like Toro mowers, Cub Cadet tractors, Husqvarna chainsaws, Echo trimmers, Briggs engines, etc.

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25M137-0019-F1 2100 model

PartsTree - Home of OEM Parts for Outdoor Power Equipment

Parts lookup and repair parts diagrams for outdoor equipment like Toro mowers, Cub Cadet tractors, Husqvarna chainsaws, Echo trimmers, Briggs engines, etc.

www.partstree.com

 

[redneckhillbilly]

check that the butterfly opens all the way, kawasaki has stops that dont allow them to open fully that you can grind off, maybe briggs did something similiar?

 

[Bob11x]

I doubt the timing would be in the flywheel- more likely a ring hear for electric start or internal magnets for a lighting coil.
These are assembly line assembled so part numbers would be a key area. Take a look at the governor springs and linkage, flywheel key, head, or head gasket??

 

[bogieboy]

Pull the intake where it meets the head, there will be a half moon restrictor plate hiding there. If it isnt there its already been de-restricted

 

[wcorey]

check that the butterfly opens all the way, kawasaki has stops that dont allow them to open fully that you can grind off, maybe briggs did something similiar?

Carb is the same part # on the IPL's so this seems unlikely.

 

[wcorey]

I doubt the timing would be in the flywheel- more likely a ring hear for electric start or internal magnets for a lighting coil.
These are assembly line assembled so part numbers would be a key area. Take a look at the governor springs and linkage, flywheel key, head, or head gasket??

Both use the same coil module and electric start components. Has an alternator for dc power, the two flywheel options could be for the different stators, though there are optional part #'s for four different stators, figuring that depends on output for options like lighting and power chute stuff. Most of these small motors depend on flywheel magnet/key position for ign timing as the trigger electronics are in the coil which is usually also in a fixed mounting position.
Entire block and head is the same and no offset flywheel key. I think they both run at the same rpm so that would seem to rule out the governor.

 

[wcorey]

Pull the intake where it meets the head, there will be a half moon restrictor plate hiding there. If it isnt there its already been de-restricted

If there is, it's not shown in the IPL, all the intake gaskets have matching part #'s on each motor. I'd like to think if it's an intake restrictor plate it would use different jets at least...

These motors are current production and have been around for 10+ years, I'd have to figure plenty of people must have experience with this by now.
Guess I'll have to dive in and have a look...

 

[wcorey]

Well sho' 'nuf...



That was too easy, would've saved me a bunch of time if I just did this to begin with...

 

[bogieboy]

Restrictor plate is how briggs has done this for years...

 

[huskihl]

Nice. I’d take an extra 3.5 hp please

 

[redneckhillbilly]

geez, thats gonna make a big difference, thanks for the pic of that.

 

[wcorey]

My only concern with removing it was how it would then affect the a/f mixture but according to the IPL's both the 1650 and 2100 share the same carb and main jet. Motor sounds good and no sign of running lean.

Apparently a lot of mopeds/scooters suffer from this as an easy way for manufacturers to comply with all the various state regulations as to what power level constitutes a non motor vehicle for tax, registration and licensing (or lack of needing) purposes.