One step forward, then a brief clatter and the engine stopped

[MickeyMoto]

wrt oil pressure, the pump feeds the crankshaft, I believe. If you have no oil pressure you will damage the crank. If it was me, I'd take off the clutch cover to be sure, but up to you! I did it once. Rebuilt the engine, used the black tube in the kit. Got cold feet, ripped it down and replaced with the original green tube. Whether you then change the clutch seals and gasket etc is another dilemma.

Looks like you have got away with the cylinder damage.

[Steve Brown]

That plug looks horrid. Is it alloy in the threads? If you fit a wire insert of the helicoil type then the result is a stainless thread and there should be no alloy in contact with the plug thread. If your re-tapping of the head was a bit rough the wire insert will not sit right and cause binding up when you fit the plug. The kit you bought would probably have a tool for removing wonky or damaged inserts. I'd be inclined to remove the insert and start again. The wire insert should wind in smoothly and so should the plug when you fit it.

[julianharty]

wrt oil pressure, the pump feeds the crankshaft, I believe. If you have no oil pressure you will damage the crank. If it was me, I'd take off the clutch cover to be sure, but up to you! I did it once. Rebuilt the engine, used the black tube in the kit. Got cold feet, ripped it down and replaced with the original green tube. Whether you then change the clutch seals and gasket etc is another dilemma.

Looks like you have got away with the cylinder damage.

The trouble with removing the cover is that I might end up with the same conundrum. Fitting the cover involves some force and that's where I think it might be possible (but hopefully not likely) for the green tube to get dislodged from the end of the oil pump. All could be well currently, so it's more of a niggle in my brain than anything else. One option is to drain the oil, then remove the cover by say 5 to 10mm and see if I can see the green tube in situ. Hmmmm...

PS: I'm very aware of the crank damage that happens when an oil pump fails, that's what happened with the 501 New York I bought via Pete Morgan when NLM's aluminium replacement for the flexible rubbery coupling broke up an jammed the gears for the oil pump The New York does have the oil pressure light and apparently that came on for the then owner but he ended up choosing to ride the bike for a few miles which destroyed the crank, bearings, and conrods.

[julianharty]

That plug looks horrid. Is it alloy in the threads? If you fit a wire insert of the helicoil type then the result is a stainless thread and there should be no alloy in contact with the plug thread. If your re-tapping of the head was a bit rough the wire insert will not sit right and cause binding up when you fit the plug. The kit you bought would probably have a tool for removing wonky or damaged inserts. I'd be inclined to remove the insert and start again. The wire insert should wind in smoothly and so should the plug when you fit it.

I don't think it's alloy in the threads, more like damage to the thread on the actual spark plug. The sealey tool works from reverse and I think it's done a pretty good job of seating the helicoil so it's no longer too tight. I'll show you when we next meet so you can take a look.

What it felt like was that the helicoil thread was slightly tight and it cut into the plug's thread. I used the provided tap (which like your kit has two thread sizes, original 14x1.25mm and the new one (probably roughly 16x1.25mm) joined by shouldered cutters that are intended to cut out the old thread entirely and create a suitable ID for the new thread. Unfortunately the kit came with instructions for perhaps an earlier version of the kit that had a single thread size and came with a 15.3mm drill bit to remove the old thread and prepare the hole.

My wire insert did wind in very smoothly which is what fooled me into thinking all was well with the repair. As I've now got a new spark plug in the head and the engine's running I'm going to leave things be for the moment rather than remove the head and replace the helicoil. I will call the supplier of the helicoil kit and have a chat with them (I didn't get the chance to do so today).

[morini_tom]

Regarding checking if the green seal is intact…

This is just a thought, I’ve never tried it and you might have to make some bench tests on a slave engine but…

What if you were to supply oil to the pump inlet by removing the mesh strainer and using a suitably sealing tube in the inlet? You might be able to measure the pressure applied. If you can do that, is it possible to measure the difference between leakage past the pump gears with a seal in place, and the pressure for leakage past them with no seal? I suspect not, but food for thought.

Second thought- what if you lay the engine on its primary drive side and put in enough oil to fill the primary drive case but not cover the oil inlet in the crankcase. Then, by removing the mesh strainer and observing the oil pump inlet while rotating the engine backwards, if the green seal is missing, the oil pump will pump oil out of the primary drive case into the oil inlet, but if the green seal is in place, other than whatever oil is in the gallery/crank, rotating backwards will yield no oil exiting from the pump inlet.

[julianharty]

Regarding checking if the green seal is intact…

This is just a thought, I’ve never tried it and you might have to make some bench tests on a slave engine but…

What if you were to supply oil to the pump inlet by removing the mesh strainer and using a suitably sealing tube in the inlet? You might be able to measure the pressure applied. If you can do that, is it possible to measure the difference between leakage past the pump gears with a seal in place, and the pressure for leakage past them with no seal? I suspect not, but food for thought.

Second thought- what if you lay the engine on its primary drive side and put in enough oil to fill the primary drive case but not cover the oil inlet in the crankcase. Then, by removing the mesh strainer and observing the oil pump inlet while rotating the engine backwards, if the green seal is missing, the oil pump will pump oil out of the primary drive case into the oil inlet, but if the green seal is in place, other than whatever oil is in the gallery/crank, rotating backwards will yield no oil exiting from the pump inlet.

Thank you Tom for both these interesting approaches. I'll have a think about how to try these ideas. I've a couple of spare engines to hand (not to sacrifice by destructive testing, more for testing these ideas out). One's even a 250 2C with the clutch cover removed!

[julianharty]

Good news, so far.
After rebuilding the bike I've ended up riding it about 40 miles or so. In the process I've replaced the air mixture screws as per Mark's advice in ATG222 which improved the idling but has increased a flat spot at about 1/8 to 1/4 throttle. I'm still fettling the bike and addressing all sort of details ranging from aligning the Cibie Z beam headlight to getting the front tyre bead sorted on the rim. I do love the smoothness of the 250 engine and its willingness to rev.

If I'd got a problem with the oil pump green neoprene seal I'd have expected it to show its hand by now. Here's hoping it's in place and doing what it's supposed to do

[Vitesse]

Re the tyre it took a second tyre and over 100psi to get a Roadrider 2 to seat on my 350!

[julianharty]

Re the tyre it took a second tyre and over 100psi to get a Roadrider 2 to seat on my 350!

Indeed, I rode the bike to my friendly local bike shop and one of the mechanics removed the valve entirely and gayly inflated the tyre to 100 psi (and at times 110 psi) then let the air rush back out. He ended up using lashings of tyre soap and it took about 10 attempts before the tyre seated and stayed seated even as the air pressure reduced (previously it sometimes unseated itself as he let the pressure out). On the final go he let the air out slowly rather than quickly and he deftly refitted the valve core while the tyre was still partly inflated. He then adjusted the pressure and I was good to go. The tyre still seemed to vibrate a bit while I was riding however it was much improved and seems to have settled down as I rode it another 10 miles or so. I'd fitted the tyre on newly powder coated wheels.

Note: I haven't (yet) balanced it and we didn't do so at the motorbike shop as the mechanic had kindly given me 10 mins of his time rather than treating this as a booked in appointment, etc. Something for me to review doing as the front disc eases up (it was somewhat rusty given the lack of use and I'm 'running it in' with a set of brake pads which I'll replace when the time seems right).

He (the mechanic) was quite happy with inflating the tyre to at least 100 psi and does this regularly to seat tyres.

[julianharty]

A quick update on the problem I had fitting the spark plug into the new helicoil'd thread.

I had a very in depth conversation with one of the engineers at WTI fasteners who make the tools and inserts and learned how they make and measure the tools and the thread coils at various times during every batch run. We reached the conclusion that the most likely reason for what happened with my insert is that it wasn't fully bedded in the newly cut thread.

There are several techniques available to bed in a helicoil, including the one I ended up doing. They include:

• After winding in the helicoil, attempt to unwind it in reverse. this puts outward pressure on the helicoil thread and helps it seat. It won't (or at least shouldn't) unwind the actual helicoil.
• Apparently in the USA there's a specific tool that's used which has a specific diameter for the thread. I haven't managed to find any details online of these. I'm guessing the shank end of a suitably sized drill bit i.e. 14mm - 1.25mm = 12.75mm, or perhaps a 12.5mm and some wiggling would do.
• The Sealey thread restorer tool I used had a similar effect of pushing the helicoil threads out into the newly cut thread.

He also explained a couple more things:

Gauge tools - there are tools that accurately measure whether the threads are correctly dimensioned. They happen to sell them https://www.wti-fasteners.co.uk/products/gauges/. He routinely uses gauges, however he reckons they not generally necessary for people using their helicoils or thread repair kits.

Removing a helicoil. We discussed options of removing and fitting a replacement helicoil in my cylinder head. He reckons it'd be fine to do so and explained the technique he uses i.e. - file a small nick about 45 degrees away from the start of the top turn of the helicoil. Then use an extractor tool https://www.wti-fasteners.co.uk/product ... tor-tools/ to unwind the helicoil. Once it's removed do whatever's necessary to clean up the thread in the cylinder head and then fit a replacement helicoil.

He kindly emailed me some more information and overall I'm reminded of the joy of dealing with people who know what they're doing and make excellent quality parts and tools, etc.

[mbmm350s]

Re the tyre it took a second tyre and over 100psi to get a Roadrider 2 to seat on my 350!

Indeed, I rode the bike to my friendly local bike shop and one of the mechanics removed the valve entirely and gayly inflated the tyre to 100 psi (and at times 110 psi) then let the air rush back out. He ended up using lashings of tyre soap and it took about 10 attempts before the tyre seated and stayed seated even as the air pressure reduced (previously it sometimes unseated itself as he let the pressure out).

He (the mechanic) was quite happy with inflating the tyre to at least 100 psi and does this regularly to seat tyres.

I had the same struggle recently to properly seat a Avon Roadrider on a 250, needed 70psi but 110 psi wow. I am not sure I would have chosen Avons having tried them on a 250. Previous owner had fitted them. Clearance to lower chainguard is minimal or non existent bracket needed a tweak.
Metzelers ME22 not so much trouble and suit 250 fine


Mark

[norbert]

It´s a Conti Classic or Road Attack?
I´m delighted with this tyres. But to settle them down sometimes you need real great pressure

[julianharty]

It´s a Conti Classic or Road Attack?
I´m delighted with this tyres. But to settle them down sometimes you need real great pressure

They're yet another brand: ContiStreet https://www.continental-tyres.co.uk/b2c ... ntistreet/ 2.75" on the front and 3.00 on the rear. And now you mention it; I realise my rear tyre isn't fully seated on the rim yet so it's time to pump up the volume (of air in the tyre).