'84-50hp Just gained 10hp & never left the sofa

[kennyk]

Hi all, I have a '84-50hp 2cyl and was wondering how I could pep up my motor. Started comparing parts on BRP site and the 50hp was identical to the 60hp. Went to the Crowley site and they even list the two horsepowers on the same parts diagram. My oem manual which covers all hp models for '84 has the 60hp listed as 21 degrees max timing where as the 50 is 19 degrees. The rpm on the 60 is 5000-6000 where as the 50 is 4500-5500. Soooo, guess who will be bumping up his timing and re-propping for higher rpm this year and hopefully gaining 10 hp? I wonder if they charged more for a 60 back in '84 than a 50hp? Ken

 

[samo_ott]

Re: '84-50hp Just gained 10hp & never left the sofa

Hard to believe the 2 degrees will make 10hp. There must be something else? Tuned exhaust? Carb throats?

 

[kennyk]

Re: '84-50hp Just gained 10hp & never left the sofa

I am shocked also. I started comparing carbs, jets, orifices, manifolds, reed assemblies, all ignition componets etc on the BRP site and they were identical. I reference the Crowley site from time to time and when you plug in my model J50BELCRM it also comes up with the 60 hp models under the same diagrams. I don't know what else to think. Ken

 

[tashasdaddy]

Re: '84-50hp Just gained 10hp & never left the sofa

i agree, or it would have been recommended along time ago.

 

[JB]

Re: '84-50hp Just gained 10hp & never left the sofa

Port timing?

 

[kennyk]

Re: '84-50hp Just gained 10hp & never left the sofa

The only difference in blocks/crankcase that I can see is the models that have TE(tiller,electric). The exhaust manifolds are the same. If there was porting or tuning done on the 60 then I would think there would be a different part number for the block. Still a mystery at this point but unless I hear a good reason for not increasing my timing by two degrees I will be attempting it. Ken

 

[kennyk]

Re: '84-50hp Just gained 10hp & never left the sofa

OK I stand corrected. The BRP site does list a seperate block/crankcase between the 50hp and the 60hp. The Crowley site didn't. So the difference probably is porting or tuning on the exhaust or possibly intake. Wish I knew exactly what was different, I'd be spending the rest of my winter dremmelling the heck out of my block. Any thoughts on bumping up the timing to check the difference or is that a no no? Ken

 

[kennyk]

Re: '84-50hp Just gained 10hp & never left the sofa

oops again, the heads are also different between the 50 and 60, strange that they use the same pistons. So I guess my ideal of finding an easy 10hp gain is out the door. Would love to see the design differences between the two when then use all the same parts except the block and head. Thanks for the help guys I'm letting this die here. Ken

 

[steelespike]

Re: '84-50hp Just gained 10hp & never left the sofa

I wouldn't take messing with the timing lightly though I wouldn't think 2 degrees would make much difference either way.I think the change is in reference to the porting and and max rpm.
If you think about it its hard to believe 2 degrees would give a 20% increase by itself.
Oops it appears I'm a little late.

 

[reeldutch]

Re: '84-50hp Just gained 10hp & never left the sofa

i dont even think it will be worth it.
10 hp i dont think you will notice.

so from a 50 to a sixty to a seventy there are differences.

i think if you want more hp
i think you should get a V4.

 

[JB]

Re: '84-50hp Just gained 10hp & never left the sofa

The different head probably offers a higher compression ratio, the different block must have different port timing and there may be differences in the exhaust geometry. The timing must be to take advantage of a higher rpm torque peak.

All that sounds like it can produce a 20% increase in rated hp, but it can also produce a lower torque curve at lower rpm. Your 50 may well make more torque than the 60 at something like 2000-2500rpm.

 

[kennyk]

Re: '84-50hp Just gained 10hp & never left the sofa

JB, I appreciate your thoughts. Your explanation makes perfect sense since all the other parts seem to be interchangeable and bore and stroke are equal. I'll have to work with what I have, I still have some rpm tweaking to do to get my 5500 WOT. Ken

 

[bfi]

Re: '84-50hp Just gained 10hp & never left the sofa

What about Boysen reeds for your easy performance increase?

 

[Silvertip]

Re: '84-50hp Just gained 10hp & never left the sofa

Bumping up ignition timing without considering carburetion, exhust tuning, and port timing is a recipe for a holed piston. Don't you think the factory would love to have the extra power and would have done this long ago if all they had to do was bump the timing 2 degrees? But then go ahead and try it. The best you may experience is that you notice little or no difference. The worst you can experience is an engine melt-down. Seems a sad thing to do to a perfectly good engine.

 

[kennyk]

Re: '84-50hp Just gained 10hp & never left the sofa

Silvertip, bumping up the timing is what I originally thought before discovering the difference in block and head between the 50 and 60hp I would not do it now. I'll concentrate on running close to 5500 rpm instead of the 4800 I'm running now by possibly raising the motor a hole but by most likely dropping down in pitch from 15 to 13. Ken