SOHC.co.uk Forums > CB350/400

Running in advice

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Ken4004:
Hi Guys and Girls the bike is now on the road after 14 years and after a few issues with the bike running rich all good now, I just needed to move the clip on the carb needles up one notch because I ran out of adjustment on the air screw but all good now.

I have rebuilt the engine including new piston rings etc but just wondered what everyone would suggest as a reasonable running in period.

At the moment I gave covered 80 miles and kept the revs below 5000 and was considering doing this for 500 miles but am I bring a bit cautious ?

Thanks in advance Ken4004

TrickyMicky:
When you consider the small size of the pistons along with the short stroke, anything much below 5000rpm would be virtually labouring the engine, with a chance of damaging the new rings.I would raise your ceiling to 7000rpm, but without ultra-wide throttle openings for about 300 miles, and not jiust running at a constant speed.  Make good use of the gearbox, speeding up, then slowing, this tends to bed things in quite nicely. Keep a watch on the oil level, and change oil and fiulter after 500 miles.  Have fun.

Mikep328:
 The only break-in I have ever done on a vehicle of any kind was the distance from the dealer's lot to the street.  ;)  This includes personal engine rebuilds as well as new bikes.  When I bought my 400F a couple of years ago, the engine had just been shop overhauled by the previous owner (I have all the paperwork) and had literally no miles on it.  I took delivery and the first time out went to redline in the first four gears.  Front Brake sucked (now quite good) but engine was/is fabulous.  I realize there are many opinions re break-in but I've never had a problem with the "ride it like you stole it" method!   BUT...do what YOU are comfortable with!  ;)

Ken4004:
Thanks for the advice guys , I’ll take your advice and increase the rev ceiling .

A couple of years ago  I went on the Triumph factory tour ( great day out and very interesting if you like engineering ) and during the tour they showed us how they test the bikes after assembly and they ran the bike after warming up to 80 % of its power through all the gears .

This surprised me and I asked the guy conducting the tour and he said that the machining tolerances where so accurate on modern bikes that running in isn’t really necessary anymore, I think I got the 500 miles running in period from the normal first service interval on a new bike which is 500 miles.

Running in at 5000 rpm is quite tedious and as everyone knows cars have no patience and give little room on the road, I am not used to this treatment because my normal ride is a Triump 1050 and you have more road presence and have the power to get yourself out of trouble and into trouble if your not careful.

McCabe-Thiele (Ted):
Personally I think running in is essential especially if you have had a rebore or new piston rings.
Not labouring the engine and keeping the revs lower say a maximum of 5500 revs increasing this gradually over the next 500 miles or so should benefit long term.
Many car manufacturers used a special running in oil that was slightly abrasive at the factory.

The ride it as if you stole it could lead to a shorter engine liife or premature oil consumption. My understanding is that at a molecular level the contact surfaces at the bore and ring need to be smooth as they mate and work harden. Over reving too soon destroys the initial bedding in process. This has become less important with current synthetic oils and more accurate fine  machining of the bores imho.

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