Needle roller little ends

[Arthur Freeman]

Hi All,
I will shortly (months rather than days!) be rebuilding one of the Leader engines. Had a problem with the gudgeon pin circlip coming out and damaging piston and bore - not really very nice!.
Therefore I will need to have a rebore and get new pistons. I have been using Suzuki GT250 pistons, but read somewhere that the GT380 pistons might be better - any comment, recommendation?.
But whilst at a friends house (well garage actually) he had a Husqvarna engine sitting on the bench, and being curious I had a look at it. It uses a caged needle roller for the little end, and I thought that might be a good idea in the Arrow/Leader engines. Anyone familiar with this option? (I am hoping that if it is a satisfactory option, that I would still use the Suzy pistons, but stay with the standard Ariel con rods).
Another reason is that I do not have (nor have access to) a suitable adjustable reamer to fit the little end bushes.
Any comments, help etc..?
Thanks, Arthur

[nevhunter]

You need hardened small ends and a good ground finish to run caged needle rollers. They are a good idea. Watch the end float and you may need spacers if it is excessive. Most original Japanese pistons are high silicon and can run quite a small clearance compared with other alloys but you still have an iron cylinder, so don't overdo it. IF you decide to stick with the bronze bushes the best finish is a diamond boring tool done with a professional conrod boring jigger and get the conrod aligned at the same time. nev

[keith.mettam]

Hi Arthur,
Not being an Arrow expert but having some limited Suzuki knowledge, I am guessing that you presently use GT250A/B pistons which use a 14mm diameter gudgeon pin. These pistons have exactly the same Suzuki part number as the GT380 pistons so must be identical. You can check this out on the Robinson's Suzuki web site. So no advantage there.
As for caged needle roller small ends, I think it is a good way to go but in view of Nev's comments it may well cost a bit so not really be worth it on a road bike. The Suzuki GT250A/B small end eye diameter in the Suzuki con-rod is 18mm and the small end eye of the rod is 17mm in width, which may help if you were thinking of using the Suzuki caged needle roller small end bearing. The following link to the Mitaka website may prove useful as it contains piston and con rod dimensions for many makes, particularly Japanese :-

http://www.mitaka.co.uk/catalogue_index.htm

I would imagine that anyone racing an Arrow would be up to speed on this sort of conversion so hopefully some input from those guys might be forthcoming for you !

Regards,
Keith.

[keith.hodgenia]

If you get in touch with John Ellis (two stroke spares man, details in Cheval) he knows all about this common modification. He can even undertake the work involved, I believe.

[bh.sprint]

Hello,

Re the needle roller little ends - I have them in the Arrow engine - the conrods are 107 m/m length
They are Lambretta ones and have a special big end pin so they fit into the Ariel flywheel halves and a liner in the little end eye to reduce the size for the 14m/m gudgeo pins in the x7 Suzuki pistons. The big end bearing is a caged one which is supposed to be better.

The engine I'm working on at the moment also has needle roller little ends but with a longer conrod
110 m/m and a larger capacity 270 cc. I'm using Honda tsx pistons. The barrels are machined to match the pistons.
It is a bit expensive to get the work done but some of the over heating on the Leader/Arrow engine seems to come from the little end bush swelling slightly and closing onto the gudeon pin.

Brian.H.

[bh.sprint]

Arrow engine with alloy barrels and Lambretta conrods ( needle roller little ends)