timing belt change

[suzieqte1]

Hi Guys, newbie to the forum hope someone can help.
have just changed ,water pump and timing belt on my 1991 ST1100.
have put all back together ,
Started fine .
my bigest problem now is my friend said - didyou remember to Advance Timing by 3 Teeth
Say what i said ?
Does this need to be done if so why?
if not done what Damage could it cause.
Bike not been used since he said this.

 

[wjbertrand]

I think what he is referring to is advancing the crank until you are 3 teeth past the timing mark on the cam pulley. This is done just prior to snugging the idler pulley down. Since you are advancing the cams and crank together, you are not really changing the timing. This is done to achieve correct belt tensioning. I've done a couple of these timing belt changes and, at least visually, I don't see much difference in the idler pulley position from lined up with the timing marks to 3 teeth advanced. I guess you could end up with a slightly loose belt and the remote possibility of it jumping a tooth or wearing out prematurely.

 

[John OoSTerhuis]

Huh....?!?! Dunno what the heck he's talking about!

If you followed the service manual you're fine.

 

[suzieqte1]

yep i did follow the manual ,
but i did not notice the last part about advancing by 3 teeth.
what i need to know, will i have to strip all down again to Advance by 3 teeth or will it be ok without Advancing ?????
as you all know not a 5 minute job to strip down

 

[vinny]

I believe that is the job of the tension spring on the idler. The timing belts do not "stretch".

 

[Mark]

It is an interference engine...
Take the spark plugs out and see if you can rotate the engine by hand without the pistons hitting the valves.

 

[George]

I would do it again... The very minor chance of the belt slipping a tooth is just too high... That step wouldn't be in there if it wasn't necessary... Like the need to pull the engine to change out the alternator.

I have change out several belts, including TWO on my 91 silver... I've never skipped that step so can't judge long term effect.

Keep us poSTed.

 

[John OoSTerhuis]

This clip from my 'The LiST' archives explains the rationale and saves me a lot of typing:

~~~~~~~~~ Timing Belt Tensioning-TShevlin.txt ~~~~~~~~

On 4 Apr 2007, Don da Roza, STOC 5230, asked about the tensioning procedure while installing a new timing belt in an ST1100:
<snip>
<< After rotating the main drive gear a couple of times the manual states to rotate another 3 teeth past the timing mark for a new belt to set it. [Page 8-14 in my '91 factory manual] I can't seem to picture how that makes any difference as to where the mark is when you tighten up the tensioner pulley. >>

To which Tim Shevlin, STOC 1183, replied:
<snip>
<<Don, my manual is not handy here at work, but I believe that by turning the engine, slack in the belt between the crank gear and cam drive gears is taken up, and is shifted to the trailing, non-drive part of the belt where application of idler tension removes it. If this slack were allowed to remain on the drive side or between cam banks, I suspect that the release of idler spring tension would be insufficient to rotate the cams the very slight amount necessary to take up the slack, thus the belt would run loose. Note that because the idler is locked in place, it is designed not to apply constant tension (as in a cam chain-equipped engine) but only to apply initial tension to a new belt. After some run time, the new belt probably runs without tension but with little or no slack for the rest of its life.>>
~~~~~~~~~~~~~~~~~~ end of file ~~~~~~~~~~~~~~~~~~

I assume the T1/T4 and corresponding index lines on the ends of the camshafts all matched up per the manual at the end of the install.

Personally, I'd pull the cover and perform the missed step, to insure the slack on the new belt is removed.

HTH

Regards, John

 

[suzieqte1]

Thanks guys
will take on board and stripdown bike again and Advance by 3
cheers john i can confirm all did match up.

Regrds Paul

 

[George]

Paul, did you "relieve" the timing belt cover so you don't have to remove or even loosen the clutch cover? This farkle alone saves time... There are several threads which document this but, basically, yur gonna carve out some plastic in the timing cover area,,, if you haven't already.

With the cover off, set up the motor as if you had just installed the belt (idler pulley fully out of the equation), turn the engine over with the crank bolt those initial two times again, plus the requied three teeth, then loosen the idler pulley bolt to allow the spring to take up the tension.

Kind of a PITA (the radiator can be a B).

Let us know when yur done. Again.

 

[wjbertrand]

I believe that is the job of the tension spring on the idler. The timing belts do not "stretch".

Just so it's clear, the spring on the idler pulley only holds / pulls the pulley into position at initial belt installation. After the 3 tooth advance procedure, the pulley is locked down to the rear housing with a nut and the spring is no longer doing anything.

 

[vinny]

Just so it's clear, the spring on the idler pulley only holds / pulls the pulley into position at initial belt installation. After the 3 tooth advance procedure, the pulley is locked down to the rear housing with a nut and the spring is no longer doing anything.

You're right, that was implied.

 

[suzieqte1]

Hi Guys
sorry took so long to get back about my timming belt change,
i took everones advice on board as to advancing belt by 3 or not.
head was full of thought stripping down and doing again by 3 .
Contacted Honda Technical Services , as to the advancing.
They said no need to advance , they see no reason as to why they need to advance by 3.
Needless to say never stripped down , Bike Running A DREEEEEEM !!!!!!
Cheers Guys
:biker:

 

[George]

Thanks for the follow-up and good to hear Honda Tech. cold advise you,,, don't think such a call to Anaheim would have resulted in positive advice, "...you have to take it to an authorized dealer."

 

[John OoSTerhuis]

STill..... I don't know if I could sleep (much less run the ST) wondering if my timing belt was running loose. Regardless of what some (ST1100 knowledgable/experienced??) Honda tech said. Why would he disregard the Honda engineers who placed this procedure in the official service
manual? I suspect he'd answer differently if you asked him to put it in writing.

JMO FWIW YMMV

John

poSTing from my iPhone