LCGB Forums

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

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)

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

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.

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.

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...

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

Warkton Tornado No.1 wrote: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