Siegfried finished at last

Test ride perfect! Woohoo. Now pulls away like should - no more fistfulls of throttle. Exhaust has not blued so all good.

Siegfried - Dynamo fixed?

Using a 7.3mm drill bit in a drill chuck I reamed out the original M7 metric fine left hand thread. Gulp. Then, using an M8 1 pitch left hand tap with a 6mm spanner as lever on the square top of the tap, gently tapped a new M8 thread. Much backwards and forwards working of the tap plus a good blast of air to clear debris and the new bolt went sweetly home. In a belt and braces style I have also purchased Loctite 270 stud lock with a breakaway of 33 nm. Decided to go without this to start with and see if the bolt holds without it. No point creating a fresh nightmare if it should nonetheless slip. So here goes for a start up - in the rain.

Streetfighter San

All smiles here. After the Steam Packet oafs shoved the headlights out of alignment getting out of the horrible bike park clamp the digital speedo has worked off and on and then not at all. Traced it to a connector which was in the line of fire and which must have been damaged at the same time. Now plan MOT this week then only need circuit pass from VJMC for WSBK at Donington for Sunday parade laps behind Carl Fogarty !

Sulky Siegfried

Good news and bad news I suppose. Lined up the dynamo timing correctly and tightened up with M7 left hand bolt. Despite bike in gear and cylinder head on the bolt still did not feel right. Anyway. Good news. Bike fired up 1st kick and revved properly instead of the usual sluggish response. Bad news. Motor coughed and died. Inspection of the dynamo showed the bolt had not held and the timing had slipped. Upshot is that I now know that it was the timing being out caused the problem all along. Solution. Well attempts to enlarge the M7 bore thread to M8 have literally ground to a halt. It just won't go. Searches everywhere for a left hand M7 tap have been fruitless. So I have decided to go for it with an M7 right hand tap + new MZ matching thread and length bolt + helicoil insert +lock bolt in with 33 NM breakaway Loctite 270. All is on order so let's see what happens next. Great news is that loads of little jobs also got done. Now it comes down to final cosmetics tidy up.

And here is the broken exhaust rocker arm tip

Nasty worn plain bushes in original 11mm rocker arm

Lovely needle roller bearings in correct 11mm replacement rocker arm

Possibly the largest collection of Simson AWO rocker arms in Europe

Top original 11mm holes with broken exhaust rocker.

Middle. Replacement 11mm in worn condition, side play on rocker mounts.

Bottom. Beautifully refurbished 9mm unit with new needle roller bearings, no side play and super smooth action. Trouble is case hardened steel too tough to bore out to 11mm head bolt diameter. Wolfgang took it to a machine shop in Suhl and they tried but had to give up. 

The middle one gets the nod - it'll fit straight on. If I have any more breakage then I can have the head bolts turned down to 9 mm.

The guilty party

At last all the final parts have arrived. The dynamo rotor is held in place via an M7 x 35mm left handed bolt that goes into this threaded hole. I liberally greased the brand new replacement bolt, the old one had crossed threads, and gently screwed it home by hand. The moment I applied gentle pressure to tighten it it span loose. The bolt came out with the same crossed threads as before. Inspection of the bolt hole shows the threads are chewed up. Curses. Next plan is to re thread the hole to M8 and standard metric M8 bolt. So the hunt is now on for a correct left hand tap and matching bolt.

Simson not Simpson

How I detest illiterate Americans who have plagued us with Spellchecker.

Apparently Simson has appeared somewhere on here with a P, Simpson, as in the cartoon series.

Anyway we all know we are talking about SIMSON here! 

So that's why then

Just read a letter in Classic Bike magazine which mentioned how alarmingly hot the fuel tank of a Z1300 Kawasaki 6 cylinder became on a ride through Spain. When I was in the South of France I was worried about the same thing on Ethel. In fact in stop /start traffic in Lyon it became so hot I pulled over, switched off, opened the fuel cap and let it stand for a while. The link to the Kawasaki is that both bikes have fuel injection. On the Kawasaki the injection system returns hot, unburnt fuel back to the tank. If the K75 does the same thing in similar temperatures that could explain it.