RE-tapping inlet stud on Mugello 186

[Strummer10]

Hi Guys, got an issue with a Muggy 186 engine where the inlet bolt on the highest shoulder to a PHBH 30 carb inlet is not biting into the barrel thread and just turning in the aluminium threads (think its threads knackered) and needs a re-tap in some way.

Just wondered if anyone has had a similar problem and best fix.

ALSO engine bolt is seized into frame so need a best fix to remove without breaking a lug off .

Thanks

[Watfordwhite]

With the engine bolt.
Mine was well and truly in there. I rested the bike on its side and kept on spraying the bolt/ engine mounts with WD40 for a week, then turned it over and did the same to the other side. This allowed WD to seep down the bolt. Then with two smaller nuts on one side, I finally got the bolt to turn. Then used lots of washers on the bolt to pack it out I finally managed to pull it through working from both sides to get the thing moving. The whole process was about 3 weeks to free it. But it had never been out since 1961. Good luck, it's a job and a 1/2.

Sorry can't help with the inlet. Never had the need to do one (Yet)

[Strummer10]

thanks good advice and sounds like being patient with it. Gonna have to drop the engine to re-tap the inlet bolt thread lol.

Will have to timesert or helicoil the inlet I guess, soft useless aluminium when you need it nice and tight lol

[Phil D]

If you can't wait can I recommend "Plus Gas" instead of WD 40 along with some gentle heat using a stack of washers that's what got mine out .
The "Plus Gas " really is the dogs at getting into places can't recommend it highly enough.

[Strummer10]

no real rush as someone else's bike.......but I know we are going to have to drop the engine and tap a new thread to take bolt for 30mm carb in a few weeks time. Aluminium only really works with studs into the case and then washers and nuts onto those studs. Removal of bolts after a few times is going to wear the threads out quickly. Ideally I will put a stud on as the better solution, which is possible once the engine is dropped I guess.

[Warkton Tornado No.1]

Any penetrant is going to help, but, as Phil D points out, PlusGas is excellent as are penetrating fluids from the likes of Toolstation. WD40 is primarily a 'Water Dispersant' as its name suggests.

The Mugello barrel has a blind M7 hole so it may be that drilling through carefully then tapping the longer hole may give sufficient grip length for a special, extra long M7 stud. Failing that, an M7 Helicoil will give a permanent solution, although an M7 will also allow an M6 Helicoil tap to reduce the size to M6 (same pitch & something I have done myself on occasion) to allow a high tensile M6 socket screw to be fitted. I suggest that option because an M6 Helicoiling kit may be a lot more use in general (as an investment) on a Lambretta than the less common M7 kit.

I hope that makes sense...

[Andie]

Good luck with thé bolt. I tried all sorts to get mine out, washers, heat, plus gas etc. In the end i took it in a mate's car to a light engineers/mechanic who used a press to extract it. Cheaper than all the cans of lubricant and worth every penny.

Andrew

[Strummer10]

Any penetrant is going to help, but, as Phil D points out, PlusGas is excellent as are penetrating fluids from the likes of Toolstation. WD40 is primarily a 'Water Dispersant' as its name suggests.

The Mugello barrel has a blind M7 hole so it may be that drilling through carefully then tapping the longer hole may give sufficient grip length for a special, extra long M7 stud. Failing that, an M7 Helicoil will give a permanent solution, although an M7 will also allow an M6 Helicoil tap to reduce the size to M6 (same pitch & something I have done myself on occasion) to allow a high tensile M6 socket screw to be fitted. I suggest that option because an M6 Helicoiling kit may be a lot more use in general (as an investment) on a Lambretta than the less common M7 kit.

I hope that makes sense...

Yes thanks Warkton that its useful as I haven't dealt with one before in a sensitive location, appreciated and will use the Plus Gas route