How much better is a 301 engine than a 251 engine?

[stuart-glos]

You may be aware I am running an ETZ251 engine in a ETZ301 bike and that I have two 301 engines that are both poorly (and probably beyond my skill level to fix).

I assume the easy option would be to fit the 301 barrel and piston onto the 251 engine - but is it worth it?

How much better is a 301 engine over the 251?

I believe it's a straight swap - but do I need to change anything else, such as the carb?

thanks

stuart

[breakwellmz]

Hi

Well,with a 20% increase in capacity,should come a 20% increase in torque-VERY noticeable i would say.

Get a workshop manual and go for it i say!

[Skorpion]

You may be aware I am running an ETZ251 engine in a ETZ301 bike and that I have two 301 engines that are both poorly (and probably beyond my skill level to fix).

I assume the easy option would be to fit the 301 barrel and piston onto the 251 engine - but is it worth it?

How much better is a 301 engine over the 251?

I believe it's a straight swap - but do I need to change anything else, such as the carb?

thanks

stuart

If it's a 251 engine you have the barrel and piston are a straight swap, you will only need a new cylinder base gasket, and gudgin pin circlips, carb settings are the same, you will notice the difference.

This is not a straight swap onto an ETZ250 crankcase as the crankcase mouth is narrower.

[andy1141]

Noticeable difference in power but a little less mpg same
250 55mph @500rpm 300 55mph @4000 rpm and a bit more top end

[Skorpion]

Noticeable difference in power but a little less mpg same
250 55mph @500rpm 300 55mph @4000 rpm and a bit more top end

Why would you change the gearing as the 251 is overgeared as standard.

The revs are the same at any speed 251 or 301 as the gearing is the same.

[DAVID THOMPSON]

i think his keyboard got the letters mixed up when he was typing
happens to me a lot
dave

[andy1141]

I've got Saxon 251 and had etz 301 when I travel far I like to see fuel economy and performance best frugal I found at about 5000 rpm though I am quiet heavy and carry a lot of camping kit
Not changed gearing but I think they changed porting in 1992/3

[Old Dog]

In short, the ETZ 250 is the best bike they built, and the TS250/1 the best motor, that said, a 301 is a considerable improvement over the 251 but all the ETZs are too thirsty for what they are.

I had an ETZ250 with a 301 (actually it was a 251 with a 301 topend) and it was grand, let a mate have it and it still going strong.

[Skorpion]

In short, the ETZ 250 is the best bike they built, and the TS250/1 the best motor, that said, a 301 is a considerable improvement over the 251 but all the ETZs are too thirsty for what they are.

I had an ETZ250 with a 301 (actually it was a 251 with a 301 topend) and it was grand, let a mate have it and it still going strong.

Yes I have to agree with you ETZ250 was the best bike they built, mine was fitted with the Wilf Green top end, and set up right, great bike should never have sold it.

But the TS250/1 Super 5 I had, well that had the smoothest motor ever, just like an electric motor not like the ETZ that had a slight vibration.

Wilf Green ETZ300
http://en.wikipedia.org/wiki/File:MZ_ET ... pecial.jpg

[davegsm82]

I'd say there's more than 20% difference.

I have both 251 and 301, the 251 engine went into my 301 when the crank melted at 70mph, the difference was very noticeable.

Its even more noticeable when you're dragging the trailer behind too.



Dave.