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CBR250R valve adjustment (DIY)

59K views 60 replies 31 participants last post by  jsonder 
#1 · (Edited)
Planning on doing your CBR250R valve adjustment yourself and not sure what it takes? Check out this article:

The website Motor Sport Rider (motorsportrider.net) has been replaced with a new website called Road and Trail (roadandtrail.net).

The link to the 2012 CBR250R valve adjustment procedure on the new website is 2012 Honda CBR250RA Valve Adjustment - Road and Trail

This article is very comprehensive and includes hints to make the valve adjustment procedure a little easier.
 
#5 ·
An Important Factor for the Shim Size Equation

I sent the following to the original author of the DIY valve adjustment:

"Thank you for your write up, it's been helpful. However, you may want to clarify one more thing; your equation. You write "A = B - C + D" and for the life of me I couldn't figure out why I kept coming up with the wrong shim size. The I looked at the service manual which states "A = (B - C) + D". Any mathematician will tell you those parenthesis will change your answer drastically, for it indicates a change in priority of standard problem solving operations procedure. Standard operations procedure states that you first add, then subtract, then if applicable multiply and finally divide. It's remembered this way add.subtract,multiply,divide and problem are always performed in that order regardless of where the +,-,×,÷ are found in the problem, unless of course there is a parenthetical section, in which case you perform what is in the parenthesis separate.

The way you've written the equation meas you first add C and D and then subtract B in order to get A, but that is all wrong. B should have C subtracted from it and then D is added to that number to get A. Please save the next poor mathematically educated schmuck the headache and write the equation as its found in the service manual."
 
#6 · (Edited)
Standard operations procedure states that you first add, then subtract, then if applicable multiply and finally divide. It's remembered this way add.subtract,multiply,divide and problem are always performed in that order regardless of where the +,-,×,÷ are found in the problem, unless of course there is a parenthetical section, in which case you perform what is in the parenthesis separate.
Sorry, but you have it wrong. I result is interpreted in a linear fashion, with the order is multiply, divide, add, subtract. You dont hop around at will, unless:

unless of course there is a parenthetical section, in which case you perform what is in the parenthesis separate.
Yes, but in the equation above there is no need for parentheses.

Y=5-2+3 =3+3=6

because the modifiers are interpreted linearly from left to right, so it is the same as

Y=(5-2)+3 = (3)+3=6

The parentheses in the manual are simply added to prevent people like yourself from doing the wrong thing :).

To get your original (incorrect) interpretation one would need to write the equation with parentheses to alter the linear left-right actions:

Y=5-(2+3)= 5-(5)=0

So you hop to inside the parentheses, then step back out and start at the beginning and move forward. Try it, even in excel (bleh) with a formula. I kinda do this for a living, sooo...:)

Dave
 
#10 · (Edited)
So I finally did my valve check. I'm a 2nd owner of a bike that was used and abused in the past. I have never worked on any engine before and I was a bit intimidated by this project. I called few shops and since they wanted +$200 for the check/adjustment I decided to do it my self. Thanks to the great step-by-step instructions by the OP it was quite simple process.
NOTE - I only did a check since the clearance was within spec. Changing the shims might be a whole new ball game.. i don't know...
Back to the project....the hardest part actually was removing the crank cap. I did not have the proper "Pro timing plug" wrench so I tried using a fine Canadian coins (Loonie ($1) and a Toonie ($2))...Well the Loonie just turned in to figure "8" and a Toonie fall apart in to two pieces since it's made out of two different alloys...Using a big slotted screwdriver did not work either, it just scratched the cap.
The cap was seized...
So I took a piece of stainless steel metal and grinned it in to a shape that fitted snugly in to the crankshaft cap. This worked at last...
After that it was a "smooth sailing". Thanks to the very detailed instructions it was not difficult at all.
Than again with proper tools and instructions everything is: "not that difficult"
So my valves were:
Intake: 0.15mm (both)
Exhaust 0.25mm (both)
This is at 2000km.
As a conclusion to my post, I will say that checking the valves was:
1.- a time very well spend
2. - educational
3. - money saving - with the money saved I already bought a helmet for the wife...so not much saving there....
In my humble opinion, its worth to try to this project on your own especially if you ar a newbie. If you are scared, take baby steps, try to take few fairings off and put it back on. Next time go further but stick to the procedure, do not cut corners and you will be fine.
This advice comes from a guy that never, ever touched an engine with a wrench and is an electronics,IT technician by trade.
 
#14 ·
This advice comes from a guy that never, ever touched an engine with a wrench and is an electronics,IT technician by trade.
Well done for having the courage the tinker. I find electronics baffling, it is so theoretical. I did replace a capacitor in a digital camera once, but that was just following a 'step by step' and using a soldering iron. I like metal, so melting and re-melting some solder was easy enough, but I don't understand electrical circuits.

Slightly off topic, fine tuning a modern engine is about re-programming the engine's computer which is something you may be good at.
 
#12 ·
One of the most difficult aspects of doing this job is measuring the gap properly with the feeler gauge.
It's VERY much down to feel and experience.
Is the feeler guage measurement correct when guage experience no resistance or only SLIGHT resistance. How is this judment best arrived at?
I've done these checks on a previous bike but always wondered if my measurement was done PROPERLY.

David.

PS The maths bit is a bit confusing. All you need to remember is that you are comparing the current gap to what it SHOULD be. Then taking note of the current shim size how does this shim size have to be increased/decreased to bring the gap back to the correct one.
 
#15 ·
... Is the feeler guage measurement correct when guage experience no resistance or only SLIGHT resistance. How is this judment best arrived at?...
When a given feeler gauge has a slight drag between the shim and rocker arm, and the next larger size gauge will not fit, you will have your correct measurement.

I've found that the angled feeler gauge sets are a little easier to work with on most motorcycle engines, in terms of getting an accurate fit between the shim and rocker arm. With the straight feeler gauge blades, you end up having to bend them to get them under the rocker arm, which can make it difficult to tell whether that particular gauge has a true fit, or just feels like it has a slight drag due to it being bent or bowed.
 
#17 ·
Did my valve adjustment yesterday using this online procedure.

Like Giko mentioned, I think the most difficult thing was finding a tool to remove the timing cap covers. I also made a modified tool made from aluminum. I used a nickel to remove the smaller cap. I scratched both caps up pretty good though. Guess I'll find some nice anodized replacements and a proper tool later but for now I'm good.

I would also recon to get some stands for the bike. Doing this procedure on the side stand allows the Intake rocker arm to slide back toward the shim and becomes a PITA. I didn't have any decent tweezers but I used a telescoping magnet to hold/place the shim in one hand and a piece of on plastic to push the shim down into the bucket.

Overall a good Saturday project and a good time with the bike.
 
#19 ·
I came up with a large washer that fit the larger crank cap perfectly, and a smaller washer for the timing cap. When I did the first VCI on the CBR, the original caps were so tight I had to use a drift punch just to break them loose. Needless to say they both looked like crap after that, so I replaced them with new ones, both of which got a light coat of anti-seize on the threads before reinstalling. I used a bit less than the "gorilla" torque that they like to use at the Thai Honda factory when I tightened them. :rolleyes:

It's interesting that the crank and timing caps on Honda's XR400R & XR650L models use 10 mm & 6 mm hex wrenches, instead of the $40 "special tool" that Honda sells to fit the slotted type caps used on the smaller single cylinder engines. My XR200R has the slotted caps as well. Added to that is the fact that the thread size is the same for all of these caps, so they are interchangeable between all these bikes. Of course, the caps which use the metric hex wrenches cost 2-3 times more than the slotted ones. Go figure...
 
#20 ·
I used this procedure.
Thank you for the post.
I recommend "bent" feeler gauges that can be removed from the main set so that you only have a single feeler gauge in your hand at a time.It's much easier to fit in that tight spot.
Both of my exhaust valves were 0.002" tight at 1000km.
Getting the old shims out was not a problem with a small telescopic magnet but getting them back in with a magnet was.There was NO WAY I was going to trust myself with tweesers.
 
#24 ·
I pretty much abandoned the Honda service manual and just used this guide solely. I like the older Honda manuals, but this one has too much back and forth, referring to other sections. Page 3-8 might say, "Remove widget; refer to page 12-6." You go to 12-6, and it says, " Remove watchamacallit; refer to page 3-6." And so on.

I approached this task yesterday at 14,000 miles, since I would be on a trip next month which would take me beyond the 16K mile service interval by at least a couple thousand miles. One thing I want to mention, which I haven't really heard yet, is how critical it is to use a proper width feeler gauge. I finally found locally a set of angled feeler gauges with .001" increments. I measured the intake valves at about .006", which is right on target. I measured the two exhaust valves at .006" & .008". Dutifully, I dove into doing the calculations to calculate the proper replacement shim, not stopping to think logically that this measurement would mean the valve tightened up by half! Something would be seriously amiss if this were the case, but I was confident of my measurement, and focusing on doing the math correctly and not fvck that up. I replaced the shims with the new thinner shims, and when I went back to check the new clearance, I got the same exact readings: .006" & .008". :confused:

I knew this was impossible, and that the explanation must lay somewhere in the measurement process. Just then a light bulb went on in my head. When I took the bike in for the 600 mile service and valve adjust, the shop told me the mechanic was having some problem, and had to get on the phone with Honda to resolve it. When I picked the bike up, the vague explanation the front desk guy told me was there was some problem with the feeler gauge, and if the gauge was not used just so, what was actually being measured was not the correct valve clearance. Fast forward to yesterday and my head-scratching identical pre and post-adjust readings.

My feeler gauges are angled, but not tapered. They are typical 1/2" wide gauges. When I had inserted them between shim and rocker fork, it was not a smooth feeling, more like it was catching up a bit on the back end of the insertion. The problem is, this is exactly what was happening. The shim is so close to flush with the valve spring retainer, or even recessed (?) that the wide feeler gauge hangs up on the top of the valve spring retainer instead of the shim, and the resultant measurement is that of the gap between the valve spring retainer and the rocker fork. Of course, when I put in the thinner shims, that measurement did not change, hence the identical reading even though I used shims about .005" thinner. You must use a feeler gauge narrower than the width of the shim, or about 7.48 mm. In this way, you are measuring the gap between shim and rocker fork, because the feeler is not riding up onto the valve spring retainer. The tips of tapered gauges would fit this bill. I happened to have three Motion Pro tappet feeler gauges which are narrow and angled. By doubling and even tripling up on the correct feelers to arrive at the various thicknesses, I was able to get an accurate measurement, although it was very difficult to keep multiple Motion Pro gauges together.

I decided to just start over, by replacing the original shims I had removed. When I did this, and measured the gap with the narrow feelers, the exhaust valves came in at 0.27 mm & 0.25 mm. The original shims did not need changing at 14K miles! I wonder how many people may have used a typical wide feeler gauge on an exhaust valve and measured .006" or so, put in shims .005" thinner, then buttoned it up without rechecking the clearance, and ended up with a clearance of .016" instead. It would be so easy to do.
 
#25 ·
The shim is so close to flush with the valve spring retainer, or even recessed (?) that the wide feeler gauge hangs up on the top of the valve spring retainer instead of the shim, and the resultant measurement is that of the gap between the valve spring retainer and the rocker fork.
Good catch. This is crucial! I just noticed this also a few days ago and was going to post about it. If the original shim that is in place is less than about 1.8mm, it will be recessed down inside the valve retainer and you will likely be measuring the clearance to the top of the retainer without touching the shim. It is very difficult to trim the end of the feeler guage with snips to 3mm and put a bend in it 3mm from the end so you can get it on the shim without touching the retainer. The metal of the guages is very brittle.
.
You can feel the shims with a sharp pick before you start to see if you have any that are recessed. I only have 1 that is that thin. Fortunately the 1.8mm shim from the other side still fit with some clearance so I was able to measure that one unubstructed and then just do the math. I need the 1.65mm shim I already had home, measured incorrectly as still too tight, and took back. Good thing the dealer is only a couple miles from my house. Maybe someone will make a good set of gauges that come with a narrow tip and are pre bent right on the end. These valve shims are the same as what Honda has used in the dirt bikes for years. I wonder if many dealer techs would also make the same mistake and do it wrong?
 
#26 ·
Would FG-26-T-3 on this page be suitable?

Inch Feeler Gage Sets ? Style FG at Eastern Industries

Details:

The blades in this carbon steel set taper from 1/2" to 1/4" at the tip for tight applications. 26 blades, 1/2" wide, tapered to 1/4" and 3" long. Thickness (in inches) .0015, .002, .0025, .003, .004, .005, .006, .007, .008, .009, .010, .011, .012, .013, .014, .015, .016, .017, .018,.019, .020, .021, .022, .023, .024, .025

Are any of the others suitable?
 
#28 ·
I just talked to my shop foreman at Honda, who is a real 30 expert. He feels that if you are needing a shim that is so thin that it doesn't protrude above the top of the retainer, that there is a problem with the valve or seat. But I am hearing several reports on here about shims that are recessed so I tend to think it is fairly normal for the CBR250R but he is adamant that he has not seen it before in the dirt bikes he services that have been using these shims for years. He feels that it indicates that the valve is wearing up into the seat abnormally. I have an extended warranty for 4 more years so I may let him play with my head eventually, but unless I start to see unacceptably rapid changes in the valve clearance, or my fuel economy goes down, I am not going to let them tear the engine down. The 1.65mm shim that I need comes right out of the middle of the size ranges that are available which is telling me that it is no surprise to Honda that someone might want to use that size.
 
#39 ·
Thanks for the link. But, there is no way in hell i will attempt to do this, EVER. I had a look through the instructions and my mind just stopped, I think i blacked out for a second or 2:eek:

I'm afraid to say that the day I attempt to do anything this advanced in an engine, will be the last day that vehicle will be running.

I'll stick to changing oil and chain maintenance:D.
 
#40 · (Edited)
... my mind just stopped, I think i blacked out for a second or 2:eek:.
Just don't black out when you're positioning a shim, and you'll be good. :)

The feeler gauge I found which should work is made by MSR. Google MSR 32-blade tapered feeler gauge, (Tucker Rocky P/N 34-2222) and they're all over the place for $10. When inserted to the depth of about 1 cm to get a reading between shim and rocker arm, the business end tapers from 5.2mm - 6.2mm, so it should work. They are not angled, so you'll need to give them a tweak with needle nose pliers. The blades are individually removable, which is nice for the tight working area around the head/frame. I'll provide the full set of thicknesses, which I haven't seen listed anywhere on the net. Notice that in our valve clearance range, and beyond, the increments are a nice 0.001".

0.001"
0.0015"
0.002"
0.0025"
0.0028"
0.003"
0.0035"
0.004" - 0.016" in 0.001" increments
0.018" - 0.024" in 0.002" increments
0.025"
0.026" - 0.034" in 0.002" increments
0.035"
0.040"
 
#42 · (Edited)
I'm hoping to make an attempt at this next Weekend now my feeler guages have arrived. I just need a source for something to remove the timing cap (the bikemaster cover wrench and the silver dollar not available here in the UK). Anyone here in Blighty used anything to reomove the timing cover?

Thanks.

David.

PS Bought one of these Motion Pro tools off Ebay

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=190883333952

The official Honda tool is over £50

http://www.davidsilverspares.co.uk/parts/by-part-number/part_077090010001/

Just hope the motion pro tool fits OK (not averse to a bit of Grinding if needed). Anyone use this tool?
 
#43 ·
to remove the timing cap
You don't really need to remove the timing cap for this job. Just bump the engine around via the rear wheel until the cam lobe is pointed away from the rocker. Anywhere around the circumference of the base circle of the cam is the same. You do not have to be dead on for any certain spot.
 
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