Ever change a knock sensor on a 1300?

Has anyone on the forum ever removed one of the knock sensors on a 1300? I'd like to know the size of the nut on it to go purchase the correct tool.

I have to swap mine to do a troubleshoot test for a code 26 that I'm experiencing over here on this thread.

Skip

EDIT: So the correct size is 24mm.

kinda a guess w/pic...

Skip,
I've never removed one myself, but the photo on page 5-86 in my SM shows two 10mm bolts, either standard hex bolts or flange bolts, can't tell from the photo. These bolts secure the knock sensor protector, which must be removed (as well as the connector) before removing the knock sensor. The manual doesn't describe how to remove the sensor itself, but I assume it would be apparent once the aforementioned are out of the way. It may be the protector secures the sensor in place. The bolts are torqued to 23 lbf-ft when replaced.

It looks to me like you need to invest in a Genuine Honda Service Manual for your bike. A complete set of metric sockets would be a good investment also, and much cheaper than buying them one at a time. If you're like some of us, including yours truly, you'll be replacing the 10mm socket from time to time anyway - the size most often used is the one most likely to 'disappear'. I hope you also have a reasonably good quality torque wrench also.

Good luck.

Mellow said:

kinda a guess w/pic...

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I hadn't noticed that the sensor had a hex fitting on it from the photo in the SM. If Skip splurges for a set of metric sockets he should be covered, unless the size required is larger than what is included in a typical set. It seems odd that the SM doesn't specify the size and/or torque spec for the sensor.

Don B said:

Skip,
I've never removed one myself, but the photo on page 5-86 in my SM shows two 10mm bolts, either standard hex bolts or flange bolts, can't tell from the photo. These bolts secure the knock sensor protector, which must be removed (as well as the connector) before removing the knock sensor. The manual doesn't describe how to remove the sensor itself, but I assume it would be apparent once the aforementioned are out of the way. It may be the protector secures the sensor in place. The bolts are torqued to 23 lbf-ft when replaced.

It looks to me like you need to invest in a Genuine Honda Service Manual for your bike. A complete set of metric sockets would be a good investment also, and much cheaper than buying them one at a time. If you're like some of us, including yours truly, you'll be replacing the 10mm socket from time to time anyway - the size most often used is the one most likely to 'disappear'. I hope you also have a reasonably good quality torque wrench also.

Good luck.

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Don, just last week I was down there working on it and did already have the protector off and yes they are 10mm. That sensor itself has a big nut on it that is bigger than any socket and open end/combination wrench I own. I do also own a service manual as well as a parts catalog but neither of those actually state the size of it or the tool needed.

Skip

skipcurt said:

Don, just last week I was down there working on it and did already have the protector off and yes they are 10mm. That sensor itself has a big nut on it that is bigger than any socket and open end/combination wrench I own. I do also own a service manual as well as a parts catalog but neither of those actually state the size of it or the tool needed.

Skip

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Is there room in there to measure it with your vernier caliper?

EDIT: If it's that big, is there a chance that it's the same size as the rear axle nut? I don't know offhand what size that is, but the torque spec for it is 80 lbf-ft, so it must be a biggie. If I get a chance, I'll go to my garage and try to find my rear axle nut socket.

EDIT #2: OK, I went to the garage to look, and thought I had lost it until I remembered which toolbox to look in - lol. Anyway, the socket I have for the rear axle nut is a 6-point 27mm socket. I also have a 12-point socket the same size, but the 6-point is preferable. If you don't already have one of those, you'll need it if you ever plan to R&R your rear wheel. If it won't fit your knock sensor, then it's time to measure. I got an inexpensive 6" Pittsburgh composite digital caliper with LCD display that's switchable between Metric and SAE scales at Harbor Freight sometime within the last year or two. I don't remember what it cost, but I'm sure it was less than $20 or I probably wouldn't have bought it. I try to be frugal most of the time, and I had gotten along without a vernier caliper for over 70 years, but at the price I figured that I'd treat me and my garage to this one. It is far from laboratory-quality, but is fine for my garage as long as it isn't abused or misused.

as another rider with code 26 and has not pulled the sensor (Let us know what you find, pictures needed) I would think if the book dose not show the torque then it dose not get torqued. Likely the two 10mm and protector are what holds sensor onto the eng block.

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Dave.David said:

as another rider with code 26 and has not pulled the sensor (Let us know what you find, pictures needed) I would think if the book dose not show the torque then it dose not get torqued. Likely the two 10mm and protector are what holds sensor onto the eng block.

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The manual has some general guidelines for torque values when they are not provided in the detailed procedures/diagrams... I don't have a manual or I'd point to that section.

Mellow said:

The manual has some general guidelines for torque values when they are not provided in the detailed procedures/diagrams... I don't have a manual or I'd point to that section.

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I don't have access to my manual right now, here at a sports bar in Alief watching the Astros and Yankees play ball. I looked at the section of the manual that you're referring to this morning, it's in the front of the manual in the General Info section, but unfortunately does not include the knock sensor. That's why I suggested in a previous reply to see if it may be the same size as the rear axle nut, 27mm. If it is, the torque should be 80lbf-ft, max.

See the treads in the pics of the knock sensor, I guaranty that won't take a 80 ft lbs. I don't think it could take 30 ft lbs.

Never use the size of the bolt head to determine torque.

Dave.David said:

Never use the size of the bolt head to determine torque.

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If I'm not mistaken, the thread size is what determines the recommended torque, and that is directly related to the bolt head size. I believe that you may be looking at the wrong portion of the sensor when you made this observation. I would certainly be hesitant to make the guarantee that you made, assuming that the sensor takes the same size socket (27mm) as the rear axle nut. That's my story and I'm sticking to it until someone can show me conclusively that it's wrong. Note that I stated 80lbf-ft, max, not necessarily that value, as that value is unknown to us mortals.

I'd measure the protrusion on the sensor - it looks like you might need a deep well socket and not a standard depth one. Since this is apt to be rarely used and expensive to buy, see if you can borrow the socket from Auto Zone (might take a purchase of a gallon of oil or something like that). Alternatively, plumbing supply places have 6 point hex sockets that look a lot like a technical climber's 'bong' chocks that are made of stamped steel and would be a lot cheaper than a socket. HF sockets are not expensive either.

Don B said:

If I'm not mistaken, the thread size is what determines the recommended torque, and that is directly related to the bolt head size. I believe that you may be looking at the wrong portion of the sensor when you made this observation. I would certainly be hesitant to make the guarantee that you made, assuming that the sensor takes the same size socket (27mm) as the rear axle nut. That's my story and I'm sticking to it until someone can show me conclusively that it's wrong. Note that I stated 80lbf-ft, max, not necessarily that value, as that value is unknown to us mortals.

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I stand by my statement. In this case I think it is safe to say the sensor, the microphone and 12v switch are taking up room, and placed inside the head of the bolt, making the head bigger then it needs to be.

Different grade bolts will reacte differently at the same torque.

Different metals will hold torque different.
There are meny different threads with the same bolt head size.

The bolt size, thread, pitch and type of metal should give us a idea of the torque it can handle we still have to ask about what it's going into and what the bolt is holding.

For example spark plugs all seem to have similar torque values. 5/8 or 13/16, in steal or aluminum block.

Sorry about the long reply, more and more came to mind. I'm sure I did leave out lots of technical stuff, no need for that, a engineer could say much more.

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If you don't have a caliper you can check the size using a crescent wrench and a tape measure. Not sure where it is and if you can even get a crescent wrench on it? Once you get over 1" metric and standard sockets seam to fit the same.

Skip - First, some manuals have it reversed if code 26 is left or right side. It would be easier to check continuity on both sides than swap the sensors.
With that being said, I swapped mine. It was a major PITA. One side is impossible to get to. If I remember correctly, you need a 24mm(or was it 27mm??) offset box wrench, which you cannot find. I used a SAE (almost) equivalent size that I taped up. It was the closest I could get. It wasn't worth the effort. I doubt that the sensor can go bad at all.
You either have a wiring problem, probably at harness connections, or the ECM than Stan gave you is also bad. My problem, bad ECM, was never intermittent, so I suspect your problem is with the wiring, most likely where the harnesses connect together.

Bill, I did do the wiring tests assuming I did them correctly (see 1st post in this thread). I guess I just have to continue knocking out the possibilities. Of course the swapped ECM could also be bad. The two possibilities left are swapping the sensors to verify they're ok and cleaning the 5 way tee.

I just want this fiasco over!!

Skip

I'd go after the easiest job first which is cleaning the 5-way tee.

A story: I once owned a Subaru Legacy. On a long mountain climb it overheated and started running really rough. When I finally got it to a shop they found nothing amiss. Computer had no codes, nada.
They wanted to start tearing the car apart to find the problem. On my dime. I said no, go back and re-check everything.
The problem finally turned out to be really simple. The rad fins were clogged up with fine sand from winter driving on sanded roads.
The rough running was a chafed wire in the FI harness which only happened when hot.
They found it by letting the car run and wiggling the FI harness.

All that to say that sometime the problem is easier to solve than one might think.

My '05 was getting crap fuel mileage which turned out to be the result of a loose spark plug lead. I found that because I put in new plugs. Doh!

I feel your pain man, I really do.

skipcurt said:

The two possibilities left are swapping the sensors to verify they're ok and cleaning the 5 way tee.

I just want this fiasco over!!

Skip

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Have you had a chance to check the sensors output as suggested in a previous post?

If the sensors are so problematic to swap (+ chances for damage), would it be possible to rig up jumper wiring from the left connector to the right sensor and vice versa?

The torque for the knock sensor is right there in the manual: 31 N-m or 23 lb-ft. You'll probably need a crow's-foot wrench to torque it since it doesn't look like there's enough room for a socket between the sensor and the standoffs that hold the guard in place.

The torque for the flange bolts that hold the guard on are in the General Information section.

--Mark

Okay, so I've successfully swapped the knock sensors. The hex head on the sensor is 24mm. The right side is easy compared to the left. The right side is flush with the engine and I was able to get it off with an open end wrench. There's not much room for movement of the wrench but I was able to loosen it and then remove by hand. The left side is a PITA!! The sensor is recessed in deeper and will not allow an open end. I had to remove the muffler and then I removed both flanges at the top of the header. I was then able to get enough movement from the header to be able to slip on a deep 24mm socket. Unfortunately not enough space for a handle though so I put a large pair of channel locks on the socket and was able to free it. Sometimes you just gotta do what you gotta do to get it done!

I did a quick little test in the driveway and then ran it up & down my street a few times hitting up to 5,000 rpm. The light did not come on but I'm pretty sure it will on my next ride given I haven't really fixed anything. All this just to test if the code will now switch to 25.

Skip