Running problem

[Shipleystevep]

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

[Daggs]

Was the weather noticeably different on both days ?

[Shipleystevep]

Errr, not massively. Very cold over to morecambe but a lot milder yesterday. Why?

[cgt75b]

What's the set up regards filter yes or no ? They can get bogged down if the filter needs a good clean preferably with neat petrol, and left to dry on the washing line.

All the best.

[bristolmod]

Errr, not massively. Very cold over to morecambe but a lot milder yesterday. Why?

A possibility?

V Cold air= more dense, therefore engine running weaker (more air to less fuel)

Lot milder= less dense, therefore engine running richer (less air and more fuel)

[Shipleystevep]

Filters through the air box with a 26 mm jetex. Can't remember precise jetting.
I'm going to look tomorrow, swap plug, re torque head, clean carb. Is there anything else obvious to do/check?
Cheers steve

[Daggs]

Yer what Chris said is what i was alluding to.

[cgt75b]

What airscoop have you got ?

[mick1]

Stuck rings would be my guess......

[B-Race Tuning]

Nothing changed since running well a few weeks ago? Like to think it isn't something that occurs within a few weeks but maybe back to ethanol? do like you say and clean carb but check through the whole fuel system. Simon.