Post by geoffers997 on Mar 29, 2021 16:03:02 GMT 1
Hi All, Alongside my poor running mystery which I think I'm making progress on thanks to forum member advice, I've been digging around on here and am wondering if I've got a restricted German bike on my hands.
Here is what I know:
VIN is 31k-016364 which makes it a 1983 M.T.C 31W (what is MTC?)
Exhausts are stamped 31W-14711 and 31W-14721
Carbs are both stamped 31W-00
The German logbook seems to say its 37KW which equates to 50bhp.
I think I'm answering my own question here but everything seems to point towards a 50bhp bike rather than an unrestricted 59bhp bike.
This is what I'm now wondering:
Once the bike is up and running normally, just how hard is it to release the extra 9bhp and is it worth it; I'm thinking:
Carbs: Either replace with an unrestricted set (Mikuni VM26SS / 31K-00) or can I re-jet the existing 31W-00 ones to the sizes in the Haynes manual if the bodies are the same ?
Exhausts: Again, some choices - cut the existing pipes and remove the restrictors (shame to do this as they've lovely condition); buy a set of 29L unrestricted pipes; buy a set of nice expansion pipes and keep the existing pipes for my dotage.
First step is to get it running right, then I'll decide whether its worth derestricting it or just leaving it alone and riding the thing
Post by shaunthe2nd on Mar 29, 2021 16:15:37 GMT 1
31w carb bodies same as 31k but with different jetting etc. They can be re-jetted to match the 31k unrestricted type, which I believe to be as follows:
Emulsion tubes type 345-P.0 Standard needles type 5K1 fitted 4th clip down.
Main jets 240
Pilot jets 22.5
Air screw set 1.25 turns out
Floats set to 21mm
You need to check what the internals are in your carbs to see if previously de-restricted.
RD 350 LC - 1982 - bounty like my bike in the 80's, finally got an original UK one. 31K/Aprilia RS hybrid - ex Yogi and Muttsnuts bike - my first hybrid Triumph Street Triple R (sorry!) ...and a box of bits I hope to be able to turn into a 1983 31K
Post by geoffers997 on Mar 29, 2021 16:26:50 GMT 1
Thanks Shaun - this is exactly what threw me, all the jetting you mention is as per my bike (I will however check again to be better than sure). It wasn't until I started trawling the forum looking for other info that I found out about these 31W bikes and thought 'hang on a minute.....'
There is a small part of me that is a tiny bit disappointed as I was going to buy a set of expansions if my current pipes were restricted; ah hell, maybe I'll just buy a set anyways who needs food? I'm fat enough to last a while without