WR450F - hone the bore?
Discussion
My ancient WR450F is in need of some love & attention so I've pulled it apart to replace the piston & rings (amongst other things). I'm not clear whether or not I need to hone the bore before I put the new piston in? Can't find a definitive answer online.
If I do, is one of these three-stone jobbies like this the way to go?
If I do, is one of these three-stone jobbies like this the way to go?
Tango13 said:
Does it have a steel or nikasil bore?
Good question - I'd no idea but have googled now and it suggests that they are.There are some very faint honing marks in the bore. Some people have suggested using a Scotchbrite pad.
I saw a video for a 250 rebuild (basically same engine) and they honed that, but I don't know if it's absolutely necessary/beneficial. I think you have to be extra-careful if you hone Nikasil?
Edited by CAPP0 on Sunday 28th November 18:41
Hmm, it's a very long time since I rebuilt any engines, but my plan was to put a B piston in and leave the bore as it is, as the piston/rings are a service item on these (apparently every 25 hours! not that I'm riding it in any way close to a competitive manner!). I haven't got an internal micrometer to measure it but it looks to be in good condition with no scoring or visible wear other than the faint hone marks.
This is my line of work, it will be a coated bore.
You can hone it with the tool you have posted all you want but it will not touch the bore, you need diamond stones to cut into the surface. The type of kit to hone such bores costs thousands of pounds and not many places have such kit.
Really you need to measure the bore accurately and you probably will not have the equipment to do this.
If you dont want to go down the road of sort of doing it the right way, clean the bore up with some scotch bright and WD40, check there is no cracks or coating missing and put it back together with the new piston you have.
You can hone it with the tool you have posted all you want but it will not touch the bore, you need diamond stones to cut into the surface. The type of kit to hone such bores costs thousands of pounds and not many places have such kit.
Really you need to measure the bore accurately and you probably will not have the equipment to do this.
If you dont want to go down the road of sort of doing it the right way, clean the bore up with some scotch bright and WD40, check there is no cracks or coating missing and put it back together with the new piston you have.
Cheers Chippy, that's really useful info.
I wouldn't generally cut corners or go for the cheapest option for maintenance (I can show you lots of receipts for other vehicles to prove that
) but to put all this in perspective: it's a 2004 bike, and I've had it 12 years. In that time it's only been used for green laning and the very occasional enduro practice day. It hasn't been raced or caned by any measure. I've been religious with oil/air/filter changes and general maintenance but this is the first time I've torn it down. It's been running like a sack of sh!t recently (which could be all manner of things) so I've decided to go right through it. It's worth buttons, but I had/have the choice of either spending a few hundred quid on a piston & rings, sorting the carb out, etc etc, or bunging it on a 99p eBay auction and looking for something else, but if I spent, say, £5k on another enduro bike I'd have no guarantee that I wasn't buying a(nother) lemon anyway, unless I buy something brand new, and for what I want it for and for the amount of times I use it, that doesn't make economic sense really. I'd rather spend that on the other bikes I have my eye on.
Plus, I have a man cave and the time to piddle about with it, and I don't hate doing it, so it's a bit of a pastime for me too.
I'll follow Chippy's advice above and bung it back together and report back on how it goes!
I wouldn't generally cut corners or go for the cheapest option for maintenance (I can show you lots of receipts for other vehicles to prove that
) but to put all this in perspective: it's a 2004 bike, and I've had it 12 years. In that time it's only been used for green laning and the very occasional enduro practice day. It hasn't been raced or caned by any measure. I've been religious with oil/air/filter changes and general maintenance but this is the first time I've torn it down. It's been running like a sack of sh!t recently (which could be all manner of things) so I've decided to go right through it. It's worth buttons, but I had/have the choice of either spending a few hundred quid on a piston & rings, sorting the carb out, etc etc, or bunging it on a 99p eBay auction and looking for something else, but if I spent, say, £5k on another enduro bike I'd have no guarantee that I wasn't buying a(nother) lemon anyway, unless I buy something brand new, and for what I want it for and for the amount of times I use it, that doesn't make economic sense really. I'd rather spend that on the other bikes I have my eye on.Plus, I have a man cave and the time to piddle about with it, and I don't hate doing it, so it's a bit of a pastime for me too.
I'll follow Chippy's advice above and bung it back together and report back on how it goes!
If you're not reboring and replating the bore then don't fit a B spec piston as it'll be oversized for the standard bore.
To make sure that the bore is standard sized buy a standard ring and put it down the borein 10mm increments measuring the ring gap each time.
If the ring gap is in spec with a new standard ring then that tells you to fit a standard new piston kit not a B size.
To make sure that the bore is standard sized buy a standard ring and put it down the borein 10mm increments measuring the ring gap each time.
If the ring gap is in spec with a new standard ring then that tells you to fit a standard new piston kit not a B size.
Steve Bass said:
If you're not reboring and replating the bore then don't fit a B spec piston as it'll be oversized for the standard bore.
To make sure that the bore is standard sized buy a standard ring and put it down the borein 10mm increments measuring the ring gap each time.
If the ring gap is in spec with a new standard ring then that tells you to fit a standard new piston kit not a B size.
A,B,C,D,E are just grades of pistons and are not oversize, the size difference is 0.001 of a mm To make sure that the bore is standard sized buy a standard ring and put it down the borein 10mm increments measuring the ring gap each time.
If the ring gap is in spec with a new standard ring then that tells you to fit a standard new piston kit not a B size.
The grading system is for the manufacture, they will grade the cylinders A or B depending how it comes off the hone on the day. So you could get a brand new cylinder that is a "B" and like wise "A"
You are correct in warning about the grades as if you stack the numbers up the wrong way it can seize, But as the OP has 12 years on the bore i dont think it will cause any issues
CAPP0 said:
Cheers Chippy, that's really useful info.
I wouldn't generally cut corners or go for the cheapest option for maintenance (I can show you lots of receipts for other vehicles to prove that ) but to put all this in perspective: it's a 2004 bike, and I've had it 12 years. In that time it's only been used for green laning and the very occasional enduro practice day. It hasn't been raced or caned by any measure. I've been religious with oil/air/filter changes and general maintenance but this is the first time I've torn it down. It's been running like a sack of sh!t recently (which could be all manner of things) so I've decided to go right through it. It's worth buttons, but I had/have the choice of either spending a few hundred quid on a piston & rings, sorting the carb out, etc etc, or bunging it on a 99p eBay auction and looking for something else, but if I spent, say, £5k on another enduro bike I'd have no guarantee that I wasn't buying a(nother) lemon anyway, unless I buy something brand new, and for what I want it for and for the amount of times I use it, that doesn't make economic sense really. I'd rather spend that on the other bikes I have my eye on.
Plus, I have a man cave and the time to piddle about with it, and I don't hate doing it, so it's a bit of a pastime for me too.
I'll follow Chippy's advice above and bung it back together and report back on how it goes!
I get what you are trying to do, and i fully understand why. I wouldn't generally cut corners or go for the cheapest option for maintenance (I can show you lots of receipts for other vehicles to prove that
) but to put all this in perspective: it's a 2004 bike, and I've had it 12 years. In that time it's only been used for green laning and the very occasional enduro practice day. It hasn't been raced or caned by any measure. I've been religious with oil/air/filter changes and general maintenance but this is the first time I've torn it down. It's been running like a sack of sh!t recently (which could be all manner of things) so I've decided to go right through it. It's worth buttons, but I had/have the choice of either spending a few hundred quid on a piston & rings, sorting the carb out, etc etc, or bunging it on a 99p eBay auction and looking for something else, but if I spent, say, £5k on another enduro bike I'd have no guarantee that I wasn't buying a(nother) lemon anyway, unless I buy something brand new, and for what I want it for and for the amount of times I use it, that doesn't make economic sense really. I'd rather spend that on the other bikes I have my eye on.Plus, I have a man cave and the time to piddle about with it, and I don't hate doing it, so it's a bit of a pastime for me too.
I'll follow Chippy's advice above and bung it back together and report back on how it goes!
The issue for me is every week somebody brings me a cylinder and asks us to "check it" now to do this takes a lot of time to set up the equipment and then to measure the bore it 8 different places and then to form a report on it. Most dont want to pay ! they just want me to say is it ok use it. Some cylinders (mainly 2 stoke ones) you don't have to measure it, you can see the wear, but with the 4 stroke cylinders like yours that have such short and thin skits on the piston you have to spend the time with the bore gauge to try and find the wear.
Going off a bit, what i tend to do is give it a very light touch with the diamond hone and you can see the low spots and you can see where to measure to see what the wear is like, the other thing you need to know is the clearance that the piston manufactures call for, this can and does vary between brands.
You sound like you have a handle on what you are doing, hopefully you can get it running better
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