1984 cbx750fa project

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1984 cbx750fa project

Postby dougie1962 » Mon Mar 02, 2015 5:59 am

had anyone personally had to replace alternator chain tensioner ? it looks like i will have to !! what do i have to do ?
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Re: 1984 cbx750fa project

Postby NobleHops » Tue Mar 03, 2015 1:18 am

Dougie, we're focused on the 6-cylinder CBX 1000 here, sorry to tell you. You may get your answer here but maybe not :-(.

Good luck!
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Re: 1984 cbx750fa project

Postby EMS » Tue Mar 03, 2015 8:46 am

Welcome Dougie. +1 what Nils said.

You may want to check here:

http://www.fj1200.info/CBXmotor.html

Considering the location of the alternator drive chain, I would guess replacing the tensioner will involve splitting the cases.

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Re: 1984 cbx750fa project

Postby Goss » Tue Mar 03, 2015 8:58 am

dougie1962 wrote:had anyone personally had to replace alternator chain tensioner ? it looks like i will have to !! what do i have to do ?



The problem is twofold: the chain stretches, and the tensioner is of poor design. The chain is under stress (much more than the cam chain) because the alternator has a lot of spinning mass and takes some accelerating and decelerating as the engine revs change. There is a clutch to take the worst shocks out, but the chain is not up to the job, although the same type of hyvo chain drives the cams with no problems.

Also the tensioner spring loads the slipper blade against the chain, with a ratchet to hold it tight as in most designs. Problem is once the chain stretches to its limit, the ratchet goes past the last tooth and now only the spring provides any tension and the tensioner rattles about as the engine revs change. Unfortunately, the only fix is an engine strip down to replace the chain and if the tensioner rivets are loose as in many engines, it needs to be replaced too. I think if this condition is allowed to go much further the tensioner would have gone backwards through the gearbox.

Whilst there, if you have a rumbling noise, a quick check can be easily done to see if the tensioner is beyond the last ratchet tooth...could be it’s time to order parts, or sell the bike). Remove the alternator cover (three allen screws) and try to rock the fan back and forth. If you can move it relative to the crankshaft, things are getting dangerously loose down there.

Regards

Goss

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Last edited by Goss on Wed Mar 04, 2015 7:37 am, edited 2 times in total.
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Re: 1984 cbx750fa project

Postby NobleHops » Tue Mar 03, 2015 5:56 pm

Goss wrote:
dougie1962 wrote:had anyone personally had to replace alternator chain tensioner ? it looks like i will have to !! what do i have to do ?



The problem is twofold:

...




Nice post Goss. It frankly blows my mind how much knowledge some of you guys have between your ears.
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http://www.restocycle.com Ikon shocks for your CBX! https://www.ikonshocksusa.com/collections/honda/honda-cbx1000-79-80
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Re: 1984 cbx750fa project

Postby Goss » Wed Mar 04, 2015 8:03 am

NobleHops wrote:
Nice post Goss. It frankly blows my mind how much knowledge some of you guys have between your ears.


You are too kind Nils, too many years of tinkering with motorcycles for necessity in my youth and now just for fun.

If its on two wheels, a Lotus or Jaguar then I am capable and having fun at the same time, best part is meeting like minded people (petrol heads) and having cups of tea or a few beers. 8)

Regards

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Last edited by Goss on Wed Mar 04, 2015 12:06 pm, edited 1 time in total.
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Re: 1984 cbx750fa project

Postby Jeff Bennetts » Wed Mar 04, 2015 12:02 pm

NobleHops wrote:
Goss wrote:
dougie1962 wrote:had anyone personally had to replace alternator chain tensioner ? it looks like i will have to !! what do i have to do ?



The problem is twofold:

...




Nice post Goss.
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Re: 1984 cbx750fa project

Postby swarrans » Wed Mar 04, 2015 1:42 pm

Goss wrote:
If its on two wheels, a Lotus or Jaguar then I am capable and having fun at the same time, best part is meeting like minded people (petrol heads) and having cups of tea or a few beers. 8)

Regards

Goss


We really need to meet up Goss - I have a Jag XK8 as well as the CBX so it sounds like we have a lot in common!

I went for a lovely ride today and stopped at the 1066 Greasy Spoon on the A21 for lunch and there were about 100 blokes out on a Brit Bike run.

I don't think my CBX carbs are right though so it would be great if you could ride my bike and give me your opinion....


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Re: 1984 cbx750fa project

Postby Goss » Wed Mar 04, 2015 5:46 pm

Yes definitely Simon,

I will be out in my Mk2 3.8 MOD tomorrow just to work and back but enough to blow away the cobwebs. Have my trusty old S Type in the garden now, main car for 15 years but now retired for an XF which is amazing but they are all diesels now. Tons of torque and wheel spin! Always wanted an XK but not exactly a family car, one day!

What makes you think you have a problem with the carbs? Are these the ones you had rebuilt?

Regards

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Re: 1984 cbx750fa project

Postby swarrans » Thu Mar 05, 2015 3:38 am

I think my carbs are just too lean - it is still really difficult to start and has to stay on choke for ages before it rides properly. The pilot screws were set at 1.25 to 1.5 turns out and I would really like to try them at 2.5 turns out but they have the adjustment restrictor "hats" fitted so unless I can take the float bowls off insitu I would have to remove the carbs which is something I can't quite face now!

Decent XK8 's are an incredible bargain IMHO - my 2000 model was £60K when new but is probably only "worth" £4K now! :o

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Re: 1984 cbx750fa project

Postby Goss » Thu Mar 05, 2015 5:31 am

2.5 turns out will make definitely make a difference and obviously the less fuel being burnt on choke the slower the warm up. The answer is carb removal just for a 15 minute adjustment which is a little painful but can be done on a standard Z within a couple of hours.

All Jags that age are a bargain for good reason, make sure your automatic gearbox filter and oil are changed before 90,000 miles otherwise a refurb/replacement is £2,500 which in most cases makes them uneconomical to repair which is a travesty. My S Type is like new and guess what it needs....gearbox judders in reverse and it wont get into top gear above 60mph, round town no problem. When Ford purchased Jaguar they put a piece of crap Ford 5R55N gearbox in it and said it was sealed for life, no maintenance. Wrong.

Let me know when you are thinking of meeting up, my details are in the Riders Magazine web/tech support.

Regards

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