Running problem

[Stevepshipley]

Hi, I'm pretty inexperienced with engines so be gentle
I took the top end off my sx150 few weeks ago, evidence of head gasket leaking although running well. Mugello 186. Cleaned head and piston and fitted new rings put it all back together and it ran fine. Took it steady for 50 miles then caned it to morecambe and home, round trip of about 130 miles. Ran great and I backed off at just over 60 but ran well. Went out yesterday with a group, about 60 miles round trip but it struggled over 50 mph, in fact I couldn't get over 50 really. Pulled well through the gears but just ran out of steam.
Could it be telling me I simply need to re-torque the head after recent strip down or something more sinister?
Thanks in advance

[johnnyXS]

well a head re-torque is about due so it wouldn't hurt but don't over do it Could be you've got another HG leak if you didn't skim the head . I always use a bit of liquid gasket if I suspect a potential leak problem like http://www.ebay.co.uk/itm/2-x-30-integral-Three-Bond-1104-Neo-Sealant-Yama-Bond-Suzuki-Bond-Toyota-Bond-/361230300077

Might be worth checking your tap flow rate and carb fuel bowl and filter for sediment /laquer etc blow your atomiser and jets out all the usual stuff.

[Stevepshipley]

Thanks for inputs,
Re-tourqued the head (did need it), cleaned carb and jets, checked filters.
Down the bypass, running like a good un again

[johnnyXS]

brilliant thats great news Nice and simple fix too.

[Storkfoot]

Could it be telling me I simply need to re-torque the head after recent strip down or something more sinister?

I had a Mk. 3 Mugello several years ago. Several times I got an air leak signified by black gungey deposits around the cylinder cowling. I got very frustrated with it but then thought that I'd just check that the head mating surface was flat. It wasn't, it was some way from being flat.

I resolved it with a flat surface, emery paper and about half an hour of my life.

Also, whilst I am winging about this Mugello, the Mk.3 was the one with the 4 dowels in the head. I think the dowels were 10mm but the space machined in the barrel and head to accommodate the dowels was 8mm, or something like that. That was another half an hour of my life wasted.

I had a few other issues with this Mugello. Suffice to say, I haven't bought another since

[coaster]

.......it struggled over 50 mph, in fact I couldn't get over 50 really. Pulled well through the gears but just ran out of steam.
Could it be telling me I simply need to re-torque the head after recent strip down or something more sinister?
Thanks in advance

This could also just be down to the vaguaries of 2 stroke engines, mine have always seemed to have good days and bad days. It doesn't take much of a wind to knock your top speed down to the point where you can't get into the power band.

[Stevepshipley]

I had a Mk. 3 Mugello several years ago. Several times I got an air leak signified by black gungey deposits around the cylinder cowling.

I resolved it with a flat surface, emery paper and about half an hour of my life.

That's the symptom that lead to my initial strip down, if it happens again I'll know now to check the head. Same version mugello with the dowels