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Throttle body rebuild


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So I've just been rebuilding my throttle bodies due to bush wear and leaking seals. Although this is for the Daytona side flow bodies the top feed bodies are exactly the same in detail.

So first thing to do is remove the throttle bodies which requires separating the cross supports on the bike. The top steel support fasteners come out fairly easily but the lower alloy cross brace held by the countersunk 5mm bolts are super hard. Dont even consider removing these without heat and a lot of concentrated heat. You need a fine tip oxy torch with a hard flame. So it needs a lot of heat directly on the head of the screw for longer than is really comfortable. Forget using a small propane torch it wont be enough. Even a soft flame with the oxy isn't enough. You only need to remove 2 screws on one throttle body lower brace as this will allow both to be removed and both ends of the upper steel brace which as I said the screws remove easily.A word or warning or caution here. My advice is to use the heat as described on the L/H throttle body screws only and leave the R/H alone. Reason being is that the aluminium cross brace on the R/H side has been milled to a fairly thin section and can be damaged on the end by the conducted heat. You wont haw any issues on the L/H side as the brace is a much heavier section.     

After you remove the throttle bodies the shaft is held in buy a circlip on one side. The left needs the throttle cable sector removed first. Dont undo the nut without restraining the cable sector itself so the torque isn't transmitted through the shaft.

You also need to remove the throttle plate assy. This is the trickiest part of the job. The 2 4mm screws that hold the throttle plate have the tail end staked. You need to grind the tails off the screws so they can be removed. I did this with a die grinder and a carbon tungsten cutter and reused the screws on one set of throttle bodies but will use new Titanium screws on the other. Mark the throttle plate so you can install it in the correct orientation.(Importanto) Also try and make sure there are no distorted/damaged threads left after grinding off the staking as you dont want to damage the threads in the throttle shaft whilst unscrewing the fasteners. Best way to do this is to grind the screws down to almost flush with the the shaft and carefully remove them. If they jam up a little screw them back in and use a small right angle pick to clean up the distorted thread and try again.The shaft only has a few threads in it so it's important they aren't damaged. It's not as hard as it sounds just take time and caare removing the screws. Here's an image of the completed installation. I'll add an image of the staked screws before grinding later.

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Here's the circlip with the washer under it and under the washer is the seal.

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Hears the other side with a new seal installed just for reference. Note the orientation of the seal which looks backwards but this is the way it needs to be. Remember the vacuum is inside and the pressure ( atmospheric) is outside which is opposite to most instillation.   Half the original seals were around the wrong way and one was missing altogether on the 2 sets of throttle bodies I have done.

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Once the shaft has been removed its time to extract the old bushes. I used an old whitworth taper tap because I din't have a 9mm taper. Thread it into the bush about 5 turns and then use a drift from the opposite side on the end of the tap to knock out the bush. I use a piece of wood with a hole in it to support the TB.

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Here's what you end up with, an old bush on the tap.

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TB with bush removed.

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Next up clean out the bushing bore and apply a little grease of your choice in preparation to install the new bush.

Here's the new bushes and seals. Bushes are Glycodur brand DU bushes p/n 081008F although any standard DU 8x10x8 bush will be fine. Cost around $2 each.

The seals are Yamaha p/n 256-14997-00-(00) at around $3 each 

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I made up a simple installation tool to press the bushes in. very simple.

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Next use the tool to press in the new bush.

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New bush and seal installed.

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Repeat for the other side. Refit the shaft and seals in the correct orientation and refit the cir-clip and washer and re fit the cable sector and shaft nut supporting the sector as you tighten the nut.

So to install the throttle plate insert it in the correct orientation as you marked it during removal and install the screws loosely. Make sure the throttle plate and shaft is completely closed with the throttle plate against the throttle body bore( back off the idle screw if fitted so the plate contacts the TB bore to align the plate) then tighten the screws. I haven't staked the screws but used blue loctite on them. I've never found a throttle plate screw loose in the 3 sets I've had apart and they dont even use Loctite. The staking isn't to stop the screw loosening only to prevent it coming completely undone, so you can get a turn out of the screws before the staking stops any further rotation. There is a risk in re staking that you might bend or distort the shaft and I'm comfortable with the Loctite doing its job. I have however used some witness marks and can easily check them from time to time but I'm confident it wont be an issue.  

Later TB's have the screw heads on the upstream side of the throttle plate.

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Thats it. The only tricky part is die grinding the tails off the throttle plate screws in reality. The rest can be done easily with hand tools and a vice. You now get nice tight shafts which seal well dont drip fuel onto the engine and give a stable idle and easier TPS base setting.

Here are some options for the R/H throttle body arm ball fitting. 

Mercedes but cant remember the p/n. Requires removal of the old ball. Use if ball is worn. Handy bolt on style and works well. There are quite a few of this style available for 8mm ball and 5mm r/h threaded shaft. Plastic/metal and metal with seal. Plenty of choices. 

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Volvo part which has a releasable clip to aid removal. Volvp P/N 946703. $7US each on ebay.

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Ciao

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Hi Phil,

thanks, a very lucid and detailed explanation. I re-worked the throttle bodies of my Jackal and V11 some years ago, some additional comments based thereupon.

This is important, the butterfly valves have edges ground at an angle to fit to the throttle bodies when closed.

8 hours ago, Lucky Phil said:

Mark the throttle plate so you can install it in the correct orientation.

The original screws block a substantial amount of the cross section, the two pictures (before/after) show the difference. Using flat-headed screws frees up some of the cross section, especially if the screw is selected (or made to fit) to the diameter of the shaft.

IMAG0108_small.jpg

For those willing to go further, one half of the shaft can be removed. Freeing up even more of the cross section for increased airflow.

IMAG0106_small.jpg 

Cheers
Meinolf

 

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4 hours ago, Meinolf said:

Hi Phil,

thanks, a very lucid and detailed explanation. I re-worked the throttle bodies of my Jackal and V11 some years ago, some additional comments based thereupon.

This is important, the butterfly valves have edges ground at an angle to fit to the throttle bodies when closed.

The original screws block a substantial amount of the cross section, the two pictures (before/after) show the difference. Using flat-headed screws frees up some of the cross section, especially if the screw is selected (or made to fit) to the diameter of the shaft.

IMAG0108_small.jpg

For those willing to go further, one half of the shaft can be removed. Freeing up even more of the cross section for increased airflow.

IMAG0106_small.jpg 

Cheers
Meinolf

 

Thanks for the images of the staked screws Meinolf. I didn't measure the edges of the plates but I assumed the orientation was important probably for the reasons you mentioned. Thanks for confirming and letting us know.  The set I'm doing now I'm going to use some low profile/button head Titanium screws. I had some TI cap screws but I couldn't machine enough off the heads to get them better than the originals while still having adequate driving hex.  

Ciao

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10 hours ago, gstallons said:

Intense and incredible . Are you a machinist by trade ? How did you find these parts to begin with ?

No, I have a lathe but I'm VERY ordinary on it. Chucks the house machinist:) Aircraft engineer was my field. Researching parts is where the time goes mainly and it's often many hours involved. Fortunately I also know some very smart and experienced people. My friend told me that the bushes were standard DU steel backed, bronze coated with an additional metal-polymer coating available at any bearing shop. This of course after I'd spent hours in research:) Interestingly the old bushes after removal had a part number on the back and some sort of company logo which I couldn't identify even with a mag glass. So by chance during research I managed to source the company that made the original bushes that Weber used by the numbers and logo together.  

I figured you may as well use the originals but I have some generic bushes as well that work perfectly fine.

The Yamaha seals was just internet research and cross referencing the sizes. The size is quite common for 8mm throttle body shafts it seems. I'm more surprised Yamaha sells them as a spare part. Good one Yamaha.

My objective is to show that this can be done at home by anyone with some readily available tools. The Oxy set is the only thing and is important as I mentioned and the screws identified need a quick hit with intense heat. Weber as usual have prioritised nothing coming loose over ease of maintenance which is understandable but it makes removal in situ a real PITA.

Ciao   

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So well done, Lucky Phil!   :thumbsup:   Just stellar, your documenting this and sharing. This is exactly the kind of thread that belongs in the "How to . . ." sub-forum.

Thanks, again, :notworthy:   Lucky Phil!

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On 9/1/2020 at 11:56 AM, Lucky Phil said:

You only need to remove 2 screws on one throttle body lower brace as this will allow both to be removed and both ends of the upper steel brace which as I said the screws remove easily.

Hi,

While re-reading Phil's post one more thing came to mind.

The throttle bodies, when fastened to the braces, are not well seated in the rubber thingies (can't remember the correct term). In other words, the screws and threads in the braces don't align well. They can be forced in, but then the throttle bodies sit slightly twisted in the rubber boots (ha, memory came to the rescue). Enlarged screw holes and regular cylindrical inbus screws seating on top of the braces allow for installation without tension and offer the benefit of screw heads which won't self-destroy during the next time the TBs are removed.

Cheers

Meinolf

PS I'll post a picture when back in Germany. Just now I'm living the good life in a cafe in the old town of Limassol on Cyprus, visiting my mate's daughter and the first grandchild

 

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27 minutes ago, Meinolf said:

Hi,

While re-reading Phil's post one more thing came to mind.

The throttle bodies, when fastened to the braces, are not well seated in the rubber thingies (can't remember the correct term). In other words, the screws and threads in the braces don't align well. They can be forced in, but then the throttle bodies sit slightly twisted in the rubber boots (ha, memory came to the rescue). Enlarged screw holes and regular cylindrical inbus screws seating on top of the braces avoid allow for installation without tension and offer the benefit of screw heads which won't self-destroy during the next time the TBs are removed.

Cheers

Meinolf

PS I'll post a picture when back in Germany. Just now I'm living the good life in a cafe in the old town of Limassol on Cyprus, visiting my mate's daughter and the first grandchild

 

After reading your post Meinolf I checked my Centauro and V11 throttle bodies and Found that on the lower aluminium cross brace the Daytona uses all countersunk screws and the V11 has countersunk screws on the right side and standard cap screws on the left. Not sure if this is standard but maybe somebody has had the TB's off my old standard engine in the past and did what you suggested. I was going to refit the throttle bodies and then both cross braces so I'll look for misalignment and apply your advice.

Your first Grandchild? I'm about to have mine soon.

Ciao

 

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Hi Phil,

Countersunk is factory standard, so a PO probably recognized the problem.

Yeah, first grandchild and me becoming a semi-grandfather. So to say. And the little loves me, I bear scratches in my face as evidence:D

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19 minutes ago, Meinolf said:

Hi Phil,

Countersunk is factory standard, so a PO probably recognized the problem.

Yeah, first grandchild and me becoming a semi-grandfather. So to say. And the little loves me, I bear scratches in my face as evidence:D

Very good, congratulations. Late January for me, a grandson.

Yes it sees so. I hadn't noticed this for the 10 years I've had the bike. Interestingly Guzzi dont even list the screws in the parts manual as separate items.

Ciao

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