Rebuilding Arrow Engine

[Stu.B]

I have an Ariel Arrow Sports crank case and thinking of bringing it back to life. I have a lot of Arrow parts to build a bike. Does anyone know how I can check when this number was first registered and if it’s being used on another bike? Engine number is T 34120 G

[Roger Gwynn]

In May 1985 this engine and frame were owned by a person in Eastbourne with the registration MHC 752. It was first registered in June 1964 as a Sports Arrow. The last log book was issued in November 1988 and the last tax ran out in March 1989, so it is probably sitting in somebody's shed or has been broken up and no-one told Swansea. I do not have any later information.
However Swansea are not really bothered about engine numbers as they consider the engine to be an interchangeable part, yes you should tell them when the engine is changed but as far as they are concerned the vehicle's identity rests with the chassis or frame.

[Stu.B]

Thanks I will have a think about a rebuild !

[Richard B]

I am also rebuilding my Arrow engine due to what I can only describe as a bad clatter from the engine which is more pronounced at low revs. I started by feeling for movement in the mains and big ends but could not detect any movement. I then found the alternator rotor was loose, (probably because the bolt had bottomed), and the keyway was was damaged. A new keyway was cut opposite the original in an attempt to maintain balance. I moved on to the primary chaincase and could find no fault. The tensioner was worn but the adjustment was correct. The gearbox was next. I found a small spring washer in the bottom, a rough bearing at the kick start end of the main shaft, a thick washer next to this bearing which resulted in offset meshing of ? second gear, and a missing spacer also on the main shaft within the kick start housing. I had high hopes of having solved the clatter. Unfortunately not. I am now dismantling the crankshaft to change all seals and bearings. I have yet to find out if I can source big ends. The three ball mains and seals should be available. I have made a tool to remove the crankcase covers. I am about to tackle a tool to hold the crankshaft still whilst I undo the 3/8 head socket screw holding the two halves of the crankshaft together. Any views on the possible cause of the clatter, gratefully received.

[Roger Gwynn]

Big-ends and the tools you are no doubt enjoying making are all available. Keep digging, yo will probably find the source of the clatter, judging by what you have found so far there will be more.

[Ivor Collins]

Have you considered piston slap as the source of the clatter? It’s very common to have some level of piston slap on these engines and would seem to fit the description you gave.
Ivor

[Richard B]

Thanks for the helpful responses. Looks like I might need to add a rebore and pistons to my list of jobs.

[Ivor Collins]

Richard
Suggest that, after inspection, you put it back together and get accustomed to a little piston slap at tickover. If it runs okay, it’s unlikely to lead to any failure and, if it’s intolerable, easy to lift off the barrel off for rebore at a later stage.

Ivor