Hi, my name is Mike and I first joined this forum in 2003. I haven't been on it for a few years...the Norton's been sitting and I've been very busy with other things. My bike is a '74 (12/73 production date) that I bought in '89 as a rolling basket case. Originally, it was the JPS color scheme with the white tank and side covers with a big blue stripe. I bought the bike for $500 with the intention having a fun project bike and not spending too much on it, but that plan quickly was replaced with the goal of a full restoration. 10 years later I had a completely disassembled bike, a powder coated frame and boxes of NOS and upgraded parts that I had aquired during the '90s.
At that point I had neither the time nor the skills to put it back together again so I found a local guy who was in the Brit bike business and contracted him to reassemble it. The end result is shown in the photo below. Pretty bike. Some of the upgrades/changes I made were that I added a Hyde forkbrace, an AP racing caliper, an 11" Hyde disc, Clubman rear sets, an NOS Norris SS cam and I also asked for the head to be shaved about .030" to give a compression of around 9.3:1. All bearings and bushings were replaced along with Mark III isos.
The bike wasn't fully sorted when I got it back and the guy who did the work closed up his shop. Over the next 10 years I'd have these periods of fits and starts when I'd be able to concentrate on it, but I never got it to run right consistently. The main problems were erratic idle and stalling in traffic, which with a kick start only bike can be a big problem. I also noticed that it vibrated a lot, especially above 4K rpm, and even though the engine and Isos had just been rebuilt, I got the feeling that there was something fundamentally wrong that was causing the vibration, and that was keeping the engine from holding a tune. A few years back I got so frustrated with it I just parked it and ignored it.
A few months ago I found another shop here in town took the bike in for a professional opinion. They got it running again and got it to idle and not stall, but also had the same thought as me, that it vibrated badly above 4K unlike a normal Norton. The vibration was so bad that it would spit gas from both carb flooding holes above 4K. So, the decision was to ride it (or sell it) like it was or tear it down and find the source of the problem. My decision was to tear it down and fix it...during the 20+ years of ownership and lots of money poured into it, I'd only had a few rides that I actually enjoyed, and I really wanted to feel what a nicely sorted Norton was like. The photo below is what it looks like right now.
Here's what we found:
1) The isos rubbers front and rear were undersized and loose in the housings, and the rubber was very hard. These were replaced as new units 10 years ago when the bike was reassembled, but maybe they were very old stock, I don't know. Also, there was no indication that they had deteriorated from the vibration...they were just small and hard. They've now been replaced with new ones that are the correct size and much softer.
2) The head was shaved down to the bottom cooling fin. The "pad" on the bottom of the head that is shaped like the head gasket was completely gone. This is probably .080" of material removed and would lead to a CR of around 10.5:1. This was clearly not my intention when I asked for a little more compression. Not exactly the best choice for a street bike and could contribute to vibration. Rather than to mess with base gaskets and thick copper head gaskets to drop the CR, I found a replacement RH10 head with stock compression.
3) After reviewing the spec sheet for the Norris SS cam and getting a few opinions on it, I recognized that it's probably a little too hot for a street bike, especially one that has erratic idle problems. It will be replaced with a JS Motorsport Stage 1 cam kit.
4) Finally, in statically balancing the pistons and rods, the shop found that one side weighed 7g more that the other. A little more inspection revealed that the pistons were identical, the rods (both big and small ends) were identical but that wrist pins were off by 7g because one was .125" shorter than the other. The short one is probably from a 750. When the engine was rebuilt in 2000, the pistons were replaced with new Hepolites so the chap doing the rebuild had to be aware that he was using two dissimilar wrist pins. Pretty shoddy work.
The crank balance will be checked and set as required and the engine reassembly should begin next week. Other changes that are being made now are that I sent the cases out to CNW for the breather mod, and I'm also going to have the JS Motorsport flatslide carbs installed.
Sorry for the long post, but this Norton has been a very long journey for me. I'm am SOOOOO looking forward to riding my smooth running and well-sorted Commando after all this time. I'll post more comments when I get the bike back.
At that point I had neither the time nor the skills to put it back together again so I found a local guy who was in the Brit bike business and contracted him to reassemble it. The end result is shown in the photo below. Pretty bike. Some of the upgrades/changes I made were that I added a Hyde forkbrace, an AP racing caliper, an 11" Hyde disc, Clubman rear sets, an NOS Norris SS cam and I also asked for the head to be shaved about .030" to give a compression of around 9.3:1. All bearings and bushings were replaced along with Mark III isos.
The bike wasn't fully sorted when I got it back and the guy who did the work closed up his shop. Over the next 10 years I'd have these periods of fits and starts when I'd be able to concentrate on it, but I never got it to run right consistently. The main problems were erratic idle and stalling in traffic, which with a kick start only bike can be a big problem. I also noticed that it vibrated a lot, especially above 4K rpm, and even though the engine and Isos had just been rebuilt, I got the feeling that there was something fundamentally wrong that was causing the vibration, and that was keeping the engine from holding a tune. A few years back I got so frustrated with it I just parked it and ignored it.
A few months ago I found another shop here in town took the bike in for a professional opinion. They got it running again and got it to idle and not stall, but also had the same thought as me, that it vibrated badly above 4K unlike a normal Norton. The vibration was so bad that it would spit gas from both carb flooding holes above 4K. So, the decision was to ride it (or sell it) like it was or tear it down and find the source of the problem. My decision was to tear it down and fix it...during the 20+ years of ownership and lots of money poured into it, I'd only had a few rides that I actually enjoyed, and I really wanted to feel what a nicely sorted Norton was like. The photo below is what it looks like right now.
Here's what we found:
1) The isos rubbers front and rear were undersized and loose in the housings, and the rubber was very hard. These were replaced as new units 10 years ago when the bike was reassembled, but maybe they were very old stock, I don't know. Also, there was no indication that they had deteriorated from the vibration...they were just small and hard. They've now been replaced with new ones that are the correct size and much softer.
2) The head was shaved down to the bottom cooling fin. The "pad" on the bottom of the head that is shaped like the head gasket was completely gone. This is probably .080" of material removed and would lead to a CR of around 10.5:1. This was clearly not my intention when I asked for a little more compression. Not exactly the best choice for a street bike and could contribute to vibration. Rather than to mess with base gaskets and thick copper head gaskets to drop the CR, I found a replacement RH10 head with stock compression.
3) After reviewing the spec sheet for the Norris SS cam and getting a few opinions on it, I recognized that it's probably a little too hot for a street bike, especially one that has erratic idle problems. It will be replaced with a JS Motorsport Stage 1 cam kit.
4) Finally, in statically balancing the pistons and rods, the shop found that one side weighed 7g more that the other. A little more inspection revealed that the pistons were identical, the rods (both big and small ends) were identical but that wrist pins were off by 7g because one was .125" shorter than the other. The short one is probably from a 750. When the engine was rebuilt in 2000, the pistons were replaced with new Hepolites so the chap doing the rebuild had to be aware that he was using two dissimilar wrist pins. Pretty shoddy work.
The crank balance will be checked and set as required and the engine reassembly should begin next week. Other changes that are being made now are that I sent the cases out to CNW for the breather mod, and I'm also going to have the JS Motorsport flatslide carbs installed.
Sorry for the long post, but this Norton has been a very long journey for me. I'm am SOOOOO looking forward to riding my smooth running and well-sorted Commando after all this time. I'll post more comments when I get the bike back.
but then again , its just ' Eager ' .
