Have you lost any coolant into the cluch/gearbox, causing the remaining coolant to boil? if so check behind your water pump impellor for corrosion and shaft seal wear!
Easy to do, just drain the coolant via the drain screw on the water pump housing. Remove the housing (you may need to get a new gasket but I did re-use mine), remove the circlip that holds on the impeller, remove the old water seal (small terminal screwdriver), check the drive shaft for wear, it should be ok, fit the new seal with the wire spring side of the seal facing out. I used a socket of the same size or slightly smaller to press the seal into position.
If the water boiled you should check that the thermostat is working and that the fan will run!!
Also if the clutch/gearbox oil is not milky then the water pump seal may be ok and you need to look at fan and thermostat first.
We had the same problem with a 2008 Rev 80, we repacked the tail pipe and the problem went away. possibly it has oiled up since you replaced the tail pipe.
We also had a misfire on a 2010 Evo 80, this time it was the cdi unit, water had got into the cdi up through the 60mm long outer cable cover.
we have now sealed the end of this so water can not enter the cdi.
I have a 300 and I have not had any starting problems hot or cold (not had to use the hot start once). The power is soft and smoooooth untill you give it a handfull and then you just hang on.
A Beta 80 would be more than powerful enough and size wise much more manageable than a 125. My sons have Beta Rev80's and they pull my 12 stone up and over banks and rocks.
The Beta Rev 80 from 2008 onward is a very capable bike from the first ride up to youth C national trials.
The web site above has info on the seat vents that need to be blocked (silicon from underside or decal from above). Info is 3/4 down on the front page.
Hope you enjoy your evo as much as I do. I can not fault it.
Just checked the valves. Spoke to an owner at the weekend who managed it without disturbing the engine - but I can't imagine how on earth he did it?
I rocked the engine forward in the frame (see picture) exposing valve covers and did the business with the clearances. A bit fiddly and I would recommend getting individual feeler gauges (mine are by WURTH) which you have to modify by bending the ends slightly (again see picture)
Clearances from Lampkins are INLET 0.10 and EXHAUST 0.15 metric.
I Removed the swinging arm and linkage today, lubed all the bearings and reassembled, the results were well worth all the effort (smooooth squeak free action ).
It has been mentioned in the beta forum that bearings have been found dry, mine were not dry but needed more grease than I found.
3. They don't change a lot generally, but performance as above can be affected dramatically by even small maladjustments. They can change through use by wear and tear / vibration / general mechanical movement etc.
Good Result Thomas well done 
).
Over heating rev3
in Beta
Posted
Have you lost any coolant into the cluch/gearbox, causing the remaining coolant to boil? if so check behind your water pump impellor for corrosion and shaft seal wear!