Suzuki 2 Strokes

Evening all ..

I've just finished a top-end rebuild on my GT250M (with a +0.5 rebore) using NOS pistons, rings, pins, small end bearings, circlips.
Started fine, ticking over very nicely, and its now ready to go out on the road again.

A question for the knowledgeable, if I may:

Running-in a re-bored engine - first time I've ever had to do this - what's the best/recommended way to do this (if there is one)?
With a redline at 8000rpm, I was thinking of doing a couple of hundred miles at max 4000rpm, then upping the ante to 5500 max for another 100 - a good plan or a recipe for disaster?

Thanks

Congrats.

Take a look at the owners manual for your bike:
https://www.oldjapanesebikes.com/mraxl_ ... /index.php

jabcd - yes I did have a look at my own copy - page 5 gives the running-in schedule for a new bike, but I'm not sure if that needs to be repeated verbatim. Something from the dim and distant past is reminding me that my Suzy-riding compatriots back in the day did little more than a week or two's gentle riding after a rebore (be it on any of the smaller twins), and after that it was business as usual.

Judging by the number of miles I do in a year, the owners handbook option is going to take me into 2023!

This is a great topic for getting lots of conflicting advice. Here is mine

Tight engines generate more heat from friction which expands things that make it even more tighter etc etc until it seizes.....

Thus, the main aim is to avoid excessive heat while rubbing off all the high/tight spots to get the engine nice and loose. To do this you can certainly follow the advised procedure in the manual. The manufacturer recommendation assumes the average 17 year old purchaser had no common sense or mechanical sensitivity so is going to be very cautious. The other way to run in is to use more rpm and power but only for very short bursts followed by a cool down ie lots of heat cycles. I start with very short bursts of full rpm in the lower gears (probably from the second run) then gradually build up from there increasing the gear/throttle/time until you no longer feel you are running in. Try to avoid any constant speed fast cruising. I would usually aim to be running full power from about 200 miles though avoiding motorway cruising for a bit longer is probably wise on a small engine. I have never seized a 2 stroke while running in (in maybe a dozen rebuilds).

My £0.02p

Keith

I have heard many different opinions on this topic. I was told by several mechanics including my local Suzuki dealer that break in isn't as important as some say. In fact they say some of the best running bikes they work on were thrashed from the start with no break in.
When I break in, I am a little gentle and don't hold a steady throttle and I don't lug the engine, like Keith said, try not to build excess heat.