CRF450R - New piston, should i hone the bore ? - Workshop

tedmagnum

09/05/2006 at 13:42

Iv got a CRF450R which iv just aquired. I got it cheap caus the owner said it prob needs a top end rebuild. The piston life is only 18 hours anyway so no big deal I thought

Iv ordered the piston kit but i was wondering if its worth honing the bore as I doubt its had a hard life.

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ST4

09/05/2006 at 14:55

I think honing gives a slightly rough surface which helps to trap oil and also helps to bed in the rings so if i'm right about that then i'd say its a good thing to do.

09/05/2006 at 17:49

I would inspect first. We had a piston out a crf450 that had done 40 hours (honda says change after 40 hours) and it was mint. Put new piston in start up and it was fine.

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KFZ

09/05/2006 at 18:09

Didnt think you should hone nikisil bores. Guzzi recomends you dont.

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ST4

09/05/2006 at 20:36

True Kev, didn't know it was nikilsil on that motor.

tedmagnum

09/05/2006 at 20:42

ST2 wrote

True Kev, didn't know it was nikilsil on that motor.

I thought nikisil plating was beign phased out as in breaks down with some kinds of petrol, something to do with suphur.. Also.........

Honing Hard Materials
In recent years, Nikasil coatings have provided a challenge for engine builders. Nikasil is a hard coating of nickel and silicon carbide about .0025Ë to .003Ë thick that is applied to cylinder bores to improve wear resistance. Invented by the German firm Mahle, Nikasil was originally developed for the Mercedes Wankel rotary engine. It has been used by BMW and Porsche in some of their engines, and is also used in many chain saw engines, some motorcycle and marine engines, and even many NASCAR Winston Cup engines.

Goodson's Jensen says PERs have had success honing Nikasil treated cylinders with diamond. But for smaller shops that have only portable honing equipment, you can't exert enough pressure with diamond to hone Nikasil. The best advice here is to use #220 silicone carbine and just do a couple of strokes to deglaze the cylinder. If a cylinder has to be bored to oversize, cut it out with a boring bar and then hone in the usual manner to achieve the desired dimensions and finish.

YOZ 450

10/05/2006 at 09:52

If it's not scored or glazed then don't.. and what ever you do don't put any oill on the piston or rings when you re assemble it. I't will smoke like a 2 stroke and burn nuff oil.

tedmagnum

10/05/2006 at 11:04

YOZ 450 wrote

If it's not scored or glazed then don't.. and what ever you do don't put any oill on the piston or rings when you re assemble it. I't will smoke like a 2 stroke and burn nuff oil.

Whys that then ? lack of oil will help the bedding in ?? Do you think it will smoke due to lack of seal ?

YOZ 450

15/05/2006 at 17:15

I'm not sure of the exact reason. The rings are different to most rings, has a corigated type between two normal ones. Oil just keeps seeping through. Oiled mine last time and would smoke untill the engine was well warm then wasn't too bad. Asked about it on thumpertalk and they discribed the exact symptoms and cure... worked a treat! no more smoke

tedmagnum

16/05/2006 at 09:31

Tomcat wrote

Glaze busting used to be the thing to do in ye olde days when replacing pistons on roadgoing fourstrokes, as an alternative to reboring. You could get a degree of tolerable wear on iron barrels (or sleeves) that on a plated one would mean replating time. On the plus side plated ones do last a lot longer before needing any attention.

In brief then, don't bother with glaze busting/honing plated barrels, they don't need it and if they are worn past limits the only answer is replating. FWIW I've changed a dozen or more 2-stroke pistons in plated bores and never once touched the bores. I would recommend oiling the rings though. A bit of smoke doesn't do any harm and it does prevent the possibility of scuffing due to dry startup and excessive friction.

Thats what I thought.. Iv ALWAYS lightly oiled the bores with new rings and never come accross any problems.

YOZ 450

16/05/2006 at 17:36

Don't say i didn't worn you....

tedmagnum

20/05/2006 at 00:22

YOZ 450 wrote

Don't say i didn't worn you....

Iv just recieved the official Honda manual for this bike. The very one written BY honda for their technicians.

They say to:

"Coat the cylinder bore, piston and piston rings with fresh engine oil prior to installation"

Just like any other engine !! I appreciate your advice all the same

ST4

20/05/2006 at 07:22

YOZ 450 wrote

I'm not sure of the exact reason. The rings are different to most rings, has a corigated type between two normal ones. Oil just keeps seeping through. Oiled mine last time and would smoke untill the engine was well warm then wasn't too bad. Asked about it on thumpertalk and they discribed the exact symptoms and cure... worked a treat! no more smoke

Thats what a typical oil control ring looks like. The idea of it is to scrape oil off the bore and drain it back into the sump.

J R 4

07/07/2012 at 00:06

Purchase the Manufactures Manuel for your model and year.

I know honda has a great manuel.

As for honeing the bore you dont have to.

Setting the piston rings in the proper alingment is more important. That can cause alot more problems and shorthen the life and performance dramaticly.

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CRF450R - New piston, should i hone the bore ?

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