Hitchcocks Forum

I have recently bought a 1952 RE 150 Ensign. I am using a 25:1 Castrol GP50 oil mix. It runs but was struggling to reach 30MPH. However, when experimented and removed the air filter it ran much better and reached 38mph. The max speed for the bike should be about 48mph so it is still not performing 100%. I have cleaned the filter but it is difficult as it is mesh in a sealed unit but appears to be fairly clean. Can anyone advise on what it going on here? Am I using the right 2 stroke oil and mixture? Is the filter OK or should this be updated? Otherwise the bike runs well in the 30mph range. It has only 4000 miles on the clock and is in great condition.

Hi Slateman welcome to 'performance' Enfields. The mixtures right, the oil is right & it sounds like you've answered you own question if the bike is 20% slower with the filter fitted. The filter should provide very little restriction to air flow. Just wash out the whole filter assy in petrol or carb. cleaner - no need to re-oil really as the 2 stroke oil will soon be in there anyway. If compression is good, other things will cause the lack of oomph. Try adjusting the timing slightly, clean carb jet & try re-positioning needle. Might seem odd but even slight brake binding & under-inflated tyres will make a big difference on such a little machine. Good luck - quite a rare machine now.
REgards, Mick.

Silencer may be full of solidified oil and carbon. Worth a wash through anyway..

Gwilly's right, decoking the silencer is important on two strokes. We used to use hot caustic soda with a potato stuck on the end to keep it in. Probably frowned on in these H&S times but it worked.
As Mickey says, there isn't a great deal of power even when running correctly so if compression is down it would rob you a few horses. Pretty quick and easy to take the bore off and check.
Has the bike been unused for some time? Crankcase seals could be suspect.
Also, your personal mass will have a bigger effect than on a larger bike.

Yea, I forget to mention the most likely cause if all else is well as Gwilly & PeteF have quite rightly pointed out if the silencer has not had a clean out. Take great care with caustic soda. It works well but as I hadn't de-coked a silencer for a long time I think I used too strong a solution recently when tried on a scooter box. My tape that I had blocked the end of the pipe with dissolved/melted emptying the 'boiling' black sludge onto the patio! Lesson learned - wear gloves -it will get HOT & find somewhere safe to empty it. I forgot about the potato plug Pete, though you might struggle to find one to fit the 'fish tailish' silencer. I like "personal mass" - I no longer wish to be a fat b*****d
REgards, Mick

Hi Micky, Gwilly and Pete F. Thanks for your advice. I will look at cleaning the silencer. I am using Super Unleaded fuel. Is this OK for the bike? Runs OK on it. I am average weight so this would not be a factor. I don't think the bike has run for years to be honest. I gather it was kept in someones house as an ornament for many years! When you say take the bore off and check, what do I need to do and look for here?

For your interest, you can view a picture of it via this link: www.slateman.co.uk/sb/images/sb-royalenfied-03.jpg Your help much appreciated. Thank you.

The image link is: www.slateman.co.uk/sb/images/sb-royalenfield-03.jpg

No point at all using super unleaded on a two stroke. If the bike has been stored inside then the crankcase seals have even more chance of drying up and getting brittle. When you get the bore off check for excessive wear on the piston, scoring on the bore, broken or gummed up rings, ridge at the upper limit of piston travel, wear on the little end, play on the big end (a little sideways play on the rod is OK) you should check the precise dimensions of the piston and bore but decent measuring tools are required for this. It should be fairly obvious if anything is in need of attention.

Whilst I agree with the necessity for precision measuring tools. If you can get a 10thou feeler gauge between the base of the piston and the bore, you really do need to check with precision tools.

Thanks PeteF. I will use 95 RON unleaded only. (I have a 1980 Triumph Spitfire and it runs really well on Super 97, no pinking at all) Despite having cleaned the air filter yesterday it still runs sweeter without it fitted. Saying this there is a slight discharge of oil/fuel back feeding through the air filter inlet. Is this right or something to do with the needle in the carb?