[CB450DCW]

I just recently purchased a 74' CB 450 K7 in "very" nice shape and after doing a little research I notice there was a Horsepower Drop in the later 450 models ? Is this due to more restrictive mufflers and leaner jetting ? If so, Is there a way to get that loss back without going to open mufflers ?

 

[tbpmusic]

I just recently purchased a 74' CB 450 K7 in "very" nice shape and after doing a little research I notice there was a Horsepower Drop in the later 450 models ? Is this due to more restrictive mufflers and leaner jetting ? If so, Is there a way to get that loss back without going to open mufflers ?

Yes to more restrictive exhaust, no to leaner jetting. Ealier 450's used 135 main jets, later models used 140 to 150 main jets.

 

[CB450DCW]

So that contributed to a 4 HP loss ?

 

[tbpmusic]

So that contributed to a 4 HP loss ?

Any published "facts" about all these twins' hp claims should be taken with a grain of salt.
The reality is that most 450's deliver 32-35 hp, 40 at most - there are exceptions, of course, but in general all hp claims from magazines or Honda are typically inflated and unrealistic.
It's likely any change in reported hp is related to differences in measuring techniques.

 

[WintrSol]

It's likely any change in reported hp is related to differences in measuring techniques.

A lot of measurements are made at the wheel with different type dynos, each with their own results. Then, those results are multiplied by a 'rule of thumb' number to get the crank horsepower. As Bill says, grain of salt. Just enjoy the acceleration you have; you probably wouldn't notice 4hp anyway.

 

[CB450DCW]

Very True. But if the Bike was jetted leaner, I would compensate for that with a little "tweaking".

On another subject, What about Electronic Ignitions ? Have a couple of Dyna systems on my other bikes and like the results.

 

[pikl]

I suggest you leave the carbs as they are on the K7. They were sold before emissions were any major concern. Most likely, it was a change to the better, than to worse. You probably do not want it to run more lean either way.



Electronic ignition is likely a good upgrade. Pamco is very popular. I have a 71' 450, but I just use points (don't mind setting them now and then, and there are also other things that need attention anyway).

 

[tbpmusic]

Very True. But if the Bike was jetted leaner, I would compensate for that with a little "tweaking".

On another subject, What about Electronic Ignitions ? Have a couple of Dyna systems on my other bikes and like the results.

Your spark plug color will tell you if you're jetted right.
If the plug color is good, DFWI.

 

[JamesPal]

The first year emissions and noise levels were mandated by the Feds for motorcycles was1977. Many of the bikes produced in 1977 were compliant. It is against the law to modify carburetors or the exhaust on any bike built after 1978. And don't remove the tag from that matress!

 

[CB450DCW]

Didn't remember what year the emissions started. I had a "New" 78' Yamaha XS750E back then and remember comparing the jetting changes made on that model year. I'll look at how the plugs are reading and if good, won't "mess" with it. I PM'd Pamco Pete about his electronic ignition, but haven't heard back from him ? Looks like he hasn't been posting on this Forum in awhile ?