G12 CENTRE WEB

moley · Post by **moley** » Sat Jul 03, 2004 5:13 pm

HELLO

IM IN PROCESS OF REBUILDING G12 MOTOR - DONE BIG END SHELLS, CENTRE WEB SHELLS NEW MAIN BEARINGS, NEW CAM BUSHES ETC.

WHEN I TRY AND PUT CRANKCASE HALFS TOGETHER THEY LOCK UP.. THEY ARE FREE ABOUT 20 THOU APART.. I HAVE COME TO THE CONCLUSION IT MUST SOMETHING RELATING TO THE CENTRE WEB BECAUSE IF I LEAVE THE WEB OUT OF THE ENGINE THE HALVES GO TOGETHER AND THE CRANK SLOPS AROUND A TREAT??

ANY IDEAS?

lawrence · Post by **lawrence** » Sat Jul 03, 2004 6:30 pm

Have you got the conrods the correct way round? On some years they were chamfered on one side to clear the crankcase. Are the spacers (name escapes me) either side of the web bearing the correct way round? I am at work [:0] so don't have the details in front of me to tell you but it does advise correct fitment in the manual. I can let you know later if you haven't a manual.

Best of luck. I start reassembling my 31csr engine in a few weeks when I have received the balanced crankshaft. Have you had yours dynamically balanced? It is the best £50 you can spend on the engine.

Lawrence [}:)]

moley · Post by **moley** » Wed Jul 07, 2004 9:17 pm

Problem solved!!

the centre web was not true!!!

i put another in which was on shelf and all bolted fine and turns over a treat!!!

lawrence · Post by **lawrence** » Wed Jul 07, 2004 11:06 pm

Congrats!

Let us know how you are getting on and any problems you encounter. hopefully then I will miss them[:)]

Lawrence [}:)]

Eric · Post by **Eric** » Fri Jul 09, 2004 10:11 pm

Lawrence where do you get your dynamic balancing done for £50.00 ?

lawrence · Post by **lawrence** » Sun Jul 11, 2004 8:41 pm

Hi Eric
Good to see you back on site again. I used Basset Down at Swindon 01793 812331. Phillip owns it and is a thoroughly nice chap. As I only live 70 miles from him I arranged to take the crank etc to him in the morning, took the wife (mine, not his) to Swindon Shopping Centre and when she had spent all her money went back to collect it. He charged me £50 (two years ago) and it is undoubtedly the best money I ever spent on a bike. Prior to balancing, the Bonnie destroyed bulbs every 100 to 150 miles and parts were always falling off or breaking. It was truly a nightmare bike, low mileage because it was impossible to keep the thing running properly.

When Philip saw the crank he said "That's not a Bonneville crank" and my heart sank! He showed me several T120 cranks he had waiting to be balanced, they were completely different. However, he got his book out and determined that mine was a batch that Triumph had tried experimentally for a short period then reverted to the previous type. When he put it on his machine the crank was perfectly in balance for static balancing i.e. on knife edges but completely out of balance dynamically. It was so bad that he wasn't sure he would be able to do it. Thankfully he could. The bike is transformed beyond my wildest dreams. Six thousand miles later I am still on all the same bulbs, the carbs have not gone out of balance, nothing has broken. All I do is routine maintenance, HOORAY!!!!

I have made an appointment to take the AJ crank in this Thursday so will let you know what his current charge is. He has told me that the AMC conrods are more demanding for balancing than the Triumph ones. Doubtless he will explain why on Thursday.

Lawrence [}:)]

Eric · Post by **Eric** » Sun Jul 11, 2004 11:58 pm

The reason I asked was that I used Basset Down a few years ago and I thought I paid about £60.00 then. I took the crank, pistons c/w rings, gudgeon pins and circlips and of course the con rods. He had specified the conrods must be within a tolerance of weight the same as each other as he was not prepared to remove metal from them to achieive balance as the balance is also along the length of the crank beside just up and down as it were. It runs like a sewing machine at about 55/60 mph and its pretty good at other speeds as well thats when its on the road anyway.