CB550k1 US Import - UK registration

[McCabe-Thiele (Ted)]

Someone here will know the best engineering solution, Timesert,  Helicoil or your solution.

Not sure if a deeper thread would change the loading on the top casing in some way that was undesirable.

[K2-K6]

You need to be careful in judging just what you have and the design that's been used originally in these crankcase.

Having a case/casting hole that has a tapped thread right up to the surface is simply a different design to one that uses a clearance bore first with the thread deeper inside the casting (the top threaded type tries to pull the surface up at the gasket, making distortion more likely) with the deeper type design aiming to avoid this.

Accuracy in understanding, with input from those on here having relevant experience of that engine, is key to understanding if it's actually damaged or designed like that in the first place.

Bolt length is absolutely critical on these, as it is for many tightly designed structures.

[juitz]

You need to be careful in judging just what you have and the design that's been used originally in these crankcase.

Having a case/casting hole that has a tapped thread right up to the surface is simply a different design to one that uses a clearance bore first with the thread deeper inside the casting (the top threaded type tries to pull the surface up at the gasket, making distortion more likely) with the deeper type design aiming to avoid this.

Accuracy in understanding, with input from those on here having relevant experience of that engine, is key to understanding if it's actually damaged or designed like that in the first place.

Bolt length is absolutely critical on these, as it is for many tightly designed structures.

Totally agree which is why as always, asking the experts.

My casings have a clearance section followed by thread. Given the load is tensile as the bolts are trying to pull the two halves together, I think the key item is to ensure the bolts have enough / same number of engaged threads to not overstress the bolt when tightening these up to approx 23Nm as per manual.

Having said that, feel like I'm missing or overlooking something here 😉

[K2-K6]

Apologies if any confusion as it's people like Bryanj and Oddjob that have  more intricate/specific knowledge than I for these engine sizes (550) to help.

General assessment though, put the corresponding bolt in through clearance crankcase side with correct washer etc, then mark (white paint) where it protrudes from face of casting and facing the other case half.
Then put that bolt into it's thread location such that you can only just feel the thread's at their very start. Now measure the distance between that original mark and the crankcase face to give you the distance the threads are now going to engage when they would be fully tightened. That figure in general fastener design should be at least 1.5x bolt diameter to take expected load.  So a 6mm bolt would need 9mm of engagement as minimum, etc for different bolt diameter.

This effectively measures by deleting the "counterbore" section to let you judge each one individually.

As mentioned, this is general engineering principle (that thread engagement length multiple) but with the provisos that there just may be some slightly different in these engines.

The risk is pulling threads out of the aluminium case without enough engagement, rather than risk to steel bolt.

[juitz]

Bit of a loss at what to do now.
120mm length bolts don't work and taking some measurements I only have about 6mm of available thread to engage.

I'm thinking keen-sert is probably only option.
I can't replace the cover as this has the engine number stamp on it.

[Bryanj]

You cant replace half a case anyway, has to be a pair. I would think a helicoil would do the job, the torque is not super high

[juitz]

I'll try a helicoil tomorrow - called a local shop and they use time-serts. Any preference one over the other?

[Laverdaroo]

I prefer the time-serts over the helicoil. Although quite dear, they're never going to move of snap etc. I had three done on the 400 cases as they were completely shot. They just feel more substantial than helicoils.

[juitz]

I prefer the time-serts over the helicoil. Although quite dear, they're never going to move of snap etc. I had three done on the 400 cases as they were completely shot. They just feel more substantial than helicoils.

Only issue is that the time-sert need a seating surface. As the case has a counterbore section, not sure I'll have enough material to drill and allow the time-sert to seat at the required depth.

[K2-K6]

A properly installed Helicoil will easily handle the torque requirements for this application. It'll not be a compromise to use this, plenty of lubricant to drill and cut the thread slowly and you'll get good tolerance on final installation.

Straight through hole such as spark plug etc you'd certainly give more consideration to timesert type repair.

[K2-K6]

Note;- you can buy Helicoil in longer length if that's more suitable to match original orientation of machining, 2.0 X instead of 1.5.

[juitz]

Note;- you can buy Helicoil in longer length if that's more suitable to match original orientation of machining, 2.0 X instead of 1.5.

Good stuff! I'll buy a kit today and order a longer length one. I was a bit confused when looking yesterday as all I could see where std ones but found the 2D, 3D options 👍

[juitz]

Hi all

Think I've got the case thread issue sorted with a helicoil. Need to get a 90mm length bolt but using a cut down 100mm one for now.

Anyway, have done my first plastigaug measurement on some of the crank journals where I have purchased new shells as per my measurements. From left to right on bottom casing as sitting on the bike I took two measurements.
brown at journal pos 1 = 0.05/0.063 then 0.038/0.063
Yellow at journal pos2 = 0.05 then 0.038/0.05
Green at journal pos4= 0.05 then 0.038
The pos3 and 5 are old shells where I think I need yellows.

The limit is 0.08mm but standard is 0.018mm to 0.048mm.

Should I stick with the shells or go with another shell colour?
 
What I'm confused about is the original shells measured 0.038mm when I plastigauged them....could it be the cold weather and parts shrinkage?

[Oddjob]

If the crank doesn't show any signs of wear and the crankcases look ok, eg shells haven't spun, they I'd stay with the colours that Honda fitted from the factory. But that's entirely up to you, never been a fan of plastigauge, far to easy to get contradictory results.

[juitz]

Thanks Ken, Crank and cases look OK so will go with what I think I need from the measurements I took.