Few cat questions

Hey just been doing some maintenance and had some concerns so thought I ask your guys opinions.
Firstly. ..
is it normal for the rear brakes to rub slightly? They are not hindering movement as far as I can tell but you can definitely hear them rubbing when you spin the wheel. Also the wheel doesn't free spin more than 1 rotation.

Secondly.....
is it ok to replace sprockets but not the chain? My rear sprocket has paint flaking off it a day just looks tatty in general and the front it clicking like am arthritic wrist but the chain is not even half maxed out yet and is in decent condition. It's a 'DID 50vm japan' whatever that means?

thirdly......
is there a secret to lubing the chain on this bike because regardless of how little I out on it still seems to fling it every which way?

And lastly.....
It has its first Mot in my ownership at the end of the month, is there anything in particular the cat is known for failing on? I've done the usual checks but just wondering if there anything particular to the cat.


Thanks for reading all that and thanks in advance for any replys

My rear wheel doesn't free spin very much..I assumed this is from the friction of the chain and front sprocket.
As for the rear pads...not sure if the rubbing is ok. (Might be a sticky pot on the caliper)

I believe it's recommended to change the chain and sprockets at the same time, since the links in a stretched chain might not fully mate up with the teeth on the new sprockets and cause additional wear. (Chains don't stretch evenly, there will be tight spots and slack spots)
Also longitudinal stretch isn't the only wear on a chain, it should also be checked for excessive side play.

I use a Scottoiler but also keep a can of chain wax (Wurth) which dries on (sort of looks like the yellowish grease you might see on your car door hinges) and isn't meant to 'fling', but I'm sure I've read of some dry products in here.

Can't think of anything that might fail an MOT.
It's only happened to me once and it wasn't even a fail. I suspected my rear tyre was marginal a couple of years ago, but after a quick visual once over the mechy told me she'd fail it if I put it in and sent me packing to get a new one fitted and bring it back.

p.s. Just got in off the bike, thought about your rear brake issue and it occurs that the grinding noise might just be a bit of grit on one of the pads.

Lube the chain the night before you use the bike. It will fling less when you come to ride the bike

Thanks for the tips. The pad are more or less brand new, less than 100 miles on them so I don't think they have any grit in. I w old expect it to be the piston not returning properly so I guess I'll have to do a re build.

I may have to look into a scottoiler as the constant cleaning is getting tiresome. Even gets up onto the underside of the seat!!

dudeofrude wrote:...Is it normal for the rear brakes to rub slightly? ...you can definitely hear them rubbing when you spin the wheel.

Check the outer edge of the disc, sometimes there will be a very narrow band of rust at the very edge on both sides and the new pads may be making contact with it. A wire brush or some emery paper will get rid of it and make things quiet again.

I have just put a scottoiler on mine but set the rate a bit lower than advised. 2 drops every three mins ISH!!!!!!
Hardly any oil flicked on the rear & chain still looks as if it's getting treat well!!!

It's quite normal to get a little rub from brake pads, although too much will cause excessive wear of the pads and disc. One way to test this is to check if the disc is extremely hot after riding and not using your rear brake, I can't advise you on how to test, I usually just burn my fingers

Before you go about rebuilding the caliper (if it ain't broke, don't try and fix it), just pop the caliper off (but still connected to the hydraulics), remove the pads and check for debris etc. Check around the pitons for any exposed dust seals (you shouldn't be able to see them), assuming all is well, get some brake cleaner or some warm soapy water and tooth brush or something of the like and give the pistons a good scrub and the area around the pistons. Then push the pistons back in (I use G-clamps to help with this) and re-install.

If the seals are exposed then these are worn and should be replaced... not a nice job on the cat due to the mono-block construction, however there is a post I placed on here a couple of years ago (I'll try and find it) of a company you can send the calipers too for rebuild for about £50 per caliper which is pretty good value.

Paul

Cheers Paul. I haven't had a chance to look yet but I will be sure to try what you said before I order any seals etc. I'm fine with caliper rebuilds, can do them in my sleep after owning a Chinese 125 through 2 winters I must have done 15 strip clean and rebuilds. That had mono block on the rear too so I'm used to fiddly. I'd say them (and possibly the kids) and the constant re bleeding are the main reason for my rapidly receding hair line haha

Also... forgot to mention I was checking the slack on the chain earlier, near the front I can push it up and touch the swing arm with it so I'm assuming it's a little slack?
Could that be the reason I'm getting the clicking from the front sprocket when I wheel it around?

I'd say them (and possibly the kids) and the constant re bleeding are the main reason for my rapidly receding hair line haha

Sounds like we must look pretty similar

The chain is definitely too slack, it shouldn't quite reach the swing arm. Worth tightening although you'll likely need to replace the front sprocket still as it sounds like the teeth are worn.

Finally got round to stripping the calipers today, was installing a rear braided hose so figured I'd go the whole hog since I was going to have to bleed them anyway.
I tried cleaning the pistons while the caliper was in one piece but discovered that one of them was completely stuck so I split the caliper and had a look. Unfortunately the seals are buggered. One of them was stuck to the piston every few mm's and is exposed even when the piston has fully returned. The other wasn't much better so gonna have to order some new ones. I've put them back together as is for the time being but the pads are still rubbing.
On the plus side, literally took me all of 30 seconds to bleed it up. Not to sound big headed but was by far the easier caliper I've ever bled even with an empty hose Haha

What method did you use to bleed them that quickly

Just the normal way?
Basically when I first put the new line on I tightened it down the master cylinder end then put my thumb over the open end and pumped the brake 3-4 times till I felt the suction on my thumb then let go and a small amount of fluid came out, so I did that again and the second time loads came out so that was primed.
Before I reassembled the caliper I poured a small amount into both bleed nipples and the little hole in some that joins the two and gave them a tap till it all disappeared inside.
Once they were back on the bike and the new hose attached I opened the bleed nipple furthest away from the master and bled from there. Literally took maybe 5 pumps/open closes and fluid was squirting out of it. Then just did the closest nipple to make sure and that threw the stuff out at me.
The only thing to note is that I did do this without the brake pads in as I was trying to test if the calipers were free moving. When one of them came out I then forced it back in so I may have pushed any trapped air back out the reservoir and inadvertently reverse bled them but I don't know.
Anyway once I put the pads in and pumped the pedal a few times it was rock hard.
Hey presto brakes bled.
I'm gonna have to do it again when the seals turn up so I'll see if it works as quick this time. I'm also gonna get the caliper powder coated so it will be completely empty and dry, might make it more of a challenge??

Am I missing something here?! You split the caliper? To my knowledge the thundercat has monoblock calipers which can't be split? Unless that's just the front ones??? Otherwise it sounds like you might an aftermarket caliper or one from a different bike like the R6?

I just remember the front ones being a pain in the arse, but don't recall doing the rear so perhaps it is different!

No the rear splits in two, the bolts are on the back of it when looking at the bike. I haven't played with the front ones yet so can't speak for them.

I'm pretty sure it's the standard one from other pictures I've seen?

I'm sure you're right, the rear is usually different, not as powerful so to speak. The front definitely don't split.. you'll have fun with those

Haha yeah they'll be the same as my Chinese 125 was, a pain in the ass. But luckily I dont have to do them yet, just gotta change the pads out for now