BSA BANTAN D1 HELP PLEASE

[degsey]

Hi Had a D1 totally rebuilt by T&G, the motor runs great, however it wont pull more than about 35 mph on the flat and any slight hill am in 2nd or 1st. what could it be ??

cheers
degsey

[peteR]

how much do you weigh?...  

[degsey]

12 stone

[Martin_UK]

I used to ride out with the late Brian Potter whose D1 trials Bantam featured on the cover of the Classic Motorcycle mag a few years ago.  

His D1 had no trouble keeping up with the bigger 500-650cc bikes at 45-55 all day long and even sped past some of us when the pub lunch stop was only a couple of miles away.

He swapped the 125 barrel for a 175 with monobloc carb and possibly tuned it a bit too so his size didn't seem to impede his Bantam's progress !!  

[G1ULZ]

Hi Had a D1 totally rebuilt by T&G, the motor runs great, however it wont pull more than about 35 mph on the flat and any slight hill am in 2nd or 1st. what could it be ??

cheers
degsey

Has  the  engine  been  rebuilt ?  may  be  it  is  still  a  bit  tight,  Is  the  Petrol /  Oil  ratio  right  and  have  you  done  a  plug  check  you  may  be  running  weak.

[degsey]

its got about 100 miles on it following a full rebuild by T & G, what oil mixture would you recommend ?

[G1ULZ]

its got about 100 miles on it following a full rebuild by T & G, what oil mixture would you recommend ?

You  will  need  to  get  some  advice  from  this  forum  has  I  have  not  had  any  experiance  with  the  new  oils  and  unleaded  petrol.  If  it  has  only  completed  100  miles  since  overhaul  then  I  think  you  are  expecting  too  much  at  this  time.

[chris p]

whats the condition of the exaust on the inside it could need decokeing also check the obvious first are the brakes binding or is the rear chain too tight

[degsey]

exhaust is clean inside

[chris p]

hi degsey im not a bantam expert but have had a few over the years first bike was a d1  is it hard to start does it emit white smoke or excessive smoke on start up i would be tempted to take head and barrell off and have a look at the rings one could be broken easy done .while top end is off check crank seals one could have been damaged on assembly again easy done has the engine been built to catalogue spec for the d1 of that year .main things in a 2 stroke for loss of power is primary compression secondry compression fuel air mixture and exaust blocked  and ignition timing  have a look at bantam racing website the guys on there are experts hope this helps

[Rex]

T&G are well-respected in the Bantam world, so I wouldn't resort to stripping thier handiwork after just 100 miles. The obvious things are carb (needle in the correct slot etc?) and/or timing ,points gap, plug etc.
Why not give T&G a ring and ask them? I'm sure they'd rather hear your concerns than have themselves potentially criticised on t'Net.

[chris p]

hi rex im not criticiseing t g but if someone got needle position or points gap wrong  what else did they do wrong

[degsey]

I don't think it is a motor rebuild problem, however I think its more a set up issue, I will ring T&G

[Goldie]

its got about 100 miles on it following a full rebuild by T & G, what oil mixture would you recommend ?

To get the correct fuel/oil ratio, there should be a measure on the fuel cap.
There is on mine.

[Searchguru]

Degsey,
I think your problems are 1. A tight, effectively, new engine.
2. Incorrect mixture, as you already suspect.
New synthetic oils are far more effective than the old mineral oils that this bike was designed to use. Therefore if you use the same ratio of fuel to oil as designated by BSA etc then you'll probably be fouling the plug, running lean and generally over oiling.
Someone out there in the two stroke world can probably give you a better idea of ratios but it will almost certainly need less than it's getting now. After a bit of a run, what does the plug look like?

If the company that re-built the bike know what they are doing then I'm sure they can advise you. I would suggest that 25:1 would be a good starting point (200 ml/cc to 5 litres of petrol) but prepare to reduce if necessary. Obviously you need to empty it out between ratio changes otherwise you'll never be sure what true ratio is best.

Incidentally a D1 is not likely to exceed 45 mph except off a cliff! That's not to say I am advocating that as I have a soft spot for them.