How-to: Clean the engine oil filter strainer.

At 7’500 miles, the service schedule dictates that the engine oil filter strainer is cleaned. This is located inside the engine, and such, is not so straightforward to get at. Small capacity engines like our beloved CBF’s, don’t tend to have much in the way of oil filtering – they rely more on regular oil changes to keep everything running smoothly and don’t have an external, throw-away filter that you replace every-other oil change, unlike bigger engines. if this small strainer gets blocked with dirt/sludge, it’s curtains for the engine. So how do we check out the internal oil filter on the CBF125? Read on…

Safety first! Engine oil is carcinogenic – so I’d advise that you wear gloves when there’s a risk of it coming into contact with your skin.

Tools and consumables used:

  • 3/8 inch breaker bar.
  • 3/8 inch torque wrench.
  • 12mm, 8mm (deep) sockets.
  • Rubber mallet.
  • Wallpaper scraper.
  • Stanley knife.
  • A small pair of pliers.
  • Paraffin.
  • Copper grease.
  • A new clutch-cover gasket.

So, we begin by draining the engine oil – which is where our 12mm socket comes in. Torque the drain bolt back up to 30Nm when you’re done. Use a new sealing washer if you can – I have had great success with a self-sealing dowty washer, available from plumber’s merchants and the like. If you’re stuck at this point, STOP and let a competent mechanic do the work!

With the engine empty of oil, we can begin! Sit yourself down so you’re looking at the right-hand side of the engine (where the exhaust is), and undo the two bolts that are holding the clutch cable retaining plate in place:

Keep those bolts safe, start arranging them on the ground in the same orientation that they came out of the engine – trust me, these engine cover bolts are different lengths.

Next, with the clutch cable plate free, gently free the end of the clutch cable:

Now remove the ten remaining engine cover bolts in a CRISS-CROSS pattern (top, bottom, side, side etc). This is important so we don’t have areas of differing stress on the engine casing, which could warp the mating surfaces. You’ll also need the deep socket here, as you can see – a normal one won’t go over the bolt head squarely.

As previously pointed out, try to arrange the bolts in such a way so that you know where they came from because there are two different lengths used. The three which sit under the cylinder barrel are shorter than the rest. This is the point where you might want to place a drip tray under the engine.

Now, grab the mallet and give a few short, sharp taps to the top and bottom of the engine cover, supporting it with your other hand as you go, until you feel the gasket seal breaking loose, and the cover coming free:

Gently remove the cover once the seal is broken – in my case the gasket was entirely left on the cover rather than the engine side. Be prepared to catch any remaining oil in your drip tray, or on the floor! Carefully remove ALL of the gasket with the wallpaper scraper and Stanley knife – being VERY VERY careful not to score or scratch the mating surface of the cover.
This gasket is made of a thin card-like material and was very stubborn when it came to scraping off every last trace of it. Persist and be patient – thanks to my good buddy, Matt, for his OCD with the Stanley knife!
Now take a little look inside the engine, the strainer is located on the lower right hand side. Carefully remove it with the help of some small pliers. Notice that if you look at it side-on, it has a ‘wedge’ shaped profile. Remember that the small end of the wedge faces inside, and the larger end faces out.
Now we can see how much crud it’s been catching, and keeping away from the working components of the engine. I was surprised to discover a considerable amount, which justifies doing this job:
Grim! Clean that lot off with some paraffin and a (old!) toothbrush or rag.
Then you’ll want to apply a little engine oil around the outside before re-inserting it:
Remember to re-insert it with the thinner end going into the engine first. Then it’s simply a case of putting a little copper grease on the end of each bolt thread (this will aid subsequent removal) before putting everything back together again. Don’t forget the gasket! And don’t forget to torque up all the bolts in a CRISS-CROSS pattern, to 10Nm each, leaving the clutch cable retaining plate bolts until last.

Author: n.martin

Managing 450-odd Macs at a university, innit.

15 thoughts on “How-to: Clean the engine oil filter strainer.”

  1. Excelent post!
    My CBF has almost 12 000km (7 500miles)… I think i’ts time to get my hands dirty!
    Nice pictures!

    1. Good man! Don’t be put off by opening the engine, it’s surprisingly accessible compared to the CG and YBR, which involved having to remove lots of other parts, like the foot rests and exhaust.

  2. Thank you so much for putting this on here.
    I have just done my filter at 10,000 miles and had a few issues.My bike had a clutch done at 800 miles under warranty at a Honda dealership.When i started to remove the bolts, i noticed some of the bolts were tighter than others, i had to shock all the bolts before i removed them by tapping them gently with a drift and a hammer , this helps with any grit around the threads that may cause the bolt to seize and snap.I started to remove the bolts in a criss cross pattern like the post before did.I came to one bolt just left of the Honda logo and this one was tighter than the rest.When i finally got it out i noticed it pulled the thread out with it. I heard the casing making some cracking sounds as the bolts were coming out. I no for absolute certain that the Honda garage that did my clutch did not use a torque wrench to do the bolts back up. When i removed the casing my oil pump pulley fell off as well. I simply just pushed back on.There is no clips or lock nuts as the casing holds the gear in. cleaned up the threads and the strain filter,( my filter was clean with hardly any grit ) replaced the gasket put it back together. Bolts were put back in a criss cross pattern and nipped up with a 1/4 ratchet.Then i torqued them in a criss cross pattern marking each bolt till i completed all of them. The bolt that pulled the threads torqued up ok, but when i need another clutch i know this thread will not hold up again. i Can’t stress enough to use a torque wrench on this type of job.and take your time doing it. No leaks so far.
    Thank you again for posted this detailed step in cleaning the filter.

  3. Good advice and an excellent site.

    Got my 2009 CBF with 11700 miles on the clock – not sure how well it’s been looked after but I intend to go through everything myself. (new to biking after 37 years of car driving – so have quite a bit of servicing knowledge and plenty of tools!).

    No problem with this job, but found it useful to have your guide on hand before the Haynes manual arrived. Pleasant surprise at how accessible a bike engine is after countless oil changes on the 4 wheeled variety. Gasket came right off with the outer cover and so quite easy to scrape clean – if some is stuck to the casing on the engine side, it would pay to make sure the scraped off bits are all cleaned out before you put the outer casing back.

    Oil strainer was suitably mucky, justifying the job in the first place. Also worth cleaning out the area below where it’s housed – quite a bit of muck had accumulated in there.

    Had to buy a new, smaller torque wrench as my existing one can’t be set low enough for the bike.

    Also changed the air filter, plug, front pads, brake fluid (definitely not changed in last two years looking at the colour!) and took the opportunity to replace the rubber brake hose with a braided steel one. Just had new Conti-Go tyres fitted at the weekend: front still had life in it, but heard nothing but horror stories about the dreaded TVS tyres.

    Next job valve clearance adjustment (have done throttle, clutch, rear brake and chain so far).
    Also may fit an in – line fuel filter when tank runs low.

    Bike idling smoothly and runs well (not really able to compare to anything though). Did what we all do and went flat out downhill to see how fast it would go – almost 80mph on the speedo, but didn’t vibrate significantly as I’ve heard at this speed.

    Thanks again for the site – keep up the good work.

  4. i own cbr 250ra ´11 and before that i had a cbr 125 ´09 , im planing to buy a cbf 125 in near future (and still keep the ´250)
    my former cbr 125 ´09 was a pian in the ass to clean filter strainer – the coolant had to be drained
    im happy to see its a bit easyer to clean strainer on the cbf.
    Does the cbf 125 use shims on valve clearance ?

  5. I have to replace my clutch plates, do you know what the tourque settings for the bolts on the pressure plate are? 🙂

  6. hi, I’ve just done some maintenance work to a 125cbf ’09, just wondered if you could answer a question for me? in the photo where you removed the oil strainer there is a black-ish cog/gear that runs off the oil pump, could you tell me (if you remember) if it connects to any other gear there? clutch or oil pump perhaps, I’ve just fitted one back together and here it doesn’t seem to match to anything?? just a free turning gear? I’m assuming right now that its a splash gear used to kick up oil from the bottom of the engine??

  7. Hello everyone!

    I’ve done that service too, and cleaned my oil filter. But after I opened the clutch casing, I found a little rubber gasket ring on the bottom. It is 10mm in diameter and looks like a standard ruber sealing ring from the store. But I couldn’t fit it anywhere. It doesn’t seem to belong anywhere inside. I’ve watched a lot of videos, where this procedure was done, but nowhere I could see such a ring nor was it mentioned. It can’t be from my tools definitely, and I found it in the oil puddle from below the engine.
    Can anybody tell me where it could be from, or whether you have seen it while cleaning the filter?

      1. Wow….that is awesome! That will be it. I wanted to check the clearances anyways, so I will have a look. Thank you for the inspiration and the quick answer!

      2. …just wanted to add, it was Nummer 3 indeed. Very glad I found it. My Honda made it for 8000 km without it, what is very interesting though. Without to be concerned. But it seems to be a blinded head venting anyways…
        Maybe this little rubber circumstance is worth to be mentioned in your other tutorial about the valve clearances?

  8. Please don’t torque up the sump, it’s unessecary – doing it by hand will be fine. I cracked my sump from this advice. Apart from that top notch info thanks 🙂

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