Author Topic: 750F2 clatter  (Read 683 times)

Offline sohc bob

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750F2 clatter
« on: August 28, 2021, 02:56:32 PM »
Hi all
Ive a 22000 mile 750 F2 and ever since ive had it it makes a lite clattering noise when ticking over at around 1100 rpm noise seems to disappear when around 2k rpm and above, it sounds louder from the clutch than any other part of the motor and makes no difference when pulling the lever, ive been told it coud be the primary chain , i always thought it was normal but ive heard other 750s that  dont do it, has any one else experienced a similar noise

Cheers bob

Offline Johnwebley

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Re: 750F2 clatter
« Reply #1 on: August 28, 2021, 03:07:46 PM »
Most Honda 4 suffer from clutch clatter,

Check,

Timings
Tappits
Carb sync

The latter should quiet the motor

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Offline sohc bob

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Re: 750F2 clatter
« Reply #2 on: August 29, 2021, 06:12:35 PM »
Hi john
Thanks for the reply the timings spot on so i will check the tappets and sync the carbs to see if this improves things

Bob

Offline Yoshi823

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Re: 750F2 clatter
« Reply #3 on: August 29, 2021, 08:59:34 PM »
Before adjusting the carbs i'd suggest doing the cam chain tension first, according to the Haynes manual.
The procedure in the owners handbook is incorrect.

I had nearly 40k on my F2 before its unfortunate demise & it always ran quietly
Bikes...they're in the blood.
Yamaha R1 2001
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Offline sohc bob

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Re: 750F2 clatter
« Reply #4 on: August 31, 2021, 08:32:59 AM »
Hi yoshi
Thanks for the reply ive already done the cam chain and timing is spot on only thing ive not done is tappets and carb sync so once these are done hopefully the clatter will lessen the bike runs great as it is but if i can quieten the noise thats only noticeable at tickover i will be a happy bunny

Bob

Online K2-K6

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Re: 750F2 clatter
« Reply #5 on: September 01, 2021, 11:03:24 AM »
As you initially note,  primary drive is normally the location of this noise but the chains don't actually wear much and so are not the highest on a list of things to firstly check through.  Gearbox and clutch rotating inertia are remote from crankshaft but linked through the primary chain, any significant oscillation from crankshaft speed changes have to also speed up and slow down the whole gearbox rotating mass via the chain which results in noise if all parts are not working in harmony.

Additional to above thread input, when you check timing have you got as close a match for cylinders 2&3 to 1&4 as possible?  You may have to compromise (within reasonable small amounts) the points gap of 2&3 to refine this pairing and so reduce initial differentiation in crankshaft pulses.

Also, carb synchronisation is principally to get the slides to match for whole range operation in parity not specifically for tickover speed. A by product of this set well is smoothness at any rpm in comparison to wrongly set sync, but adjustment is ultimately too course to finely resolve low speed running.

Honda put in their manual a specific routine to adjust low speed running.  After setting all the other items listed in this thread, then with motor warmed and idling pick one carb and turn the low speed mixture screw (it's fuel on pd carbs not air, also backwards compared to previous carbs with screwing in to lean and out to rich direction) inward to hear the engine acceleration to highest point (if you go too far it'll start to miss on that cylinder) and then from that peak rpm make it richer to bring the rpm down by 100 rpm. Then reset the overall tickover speed and repeat the routine for each subsequent cylinder until you've got setting for all four.
This trims the combustion for each cylinder to give essentially the same energy burn regardless of equipment variance to keep crankshaft pulses in equilibrium, and how the factory set them. They also note to record the final position as datum for future reference.

This should give the most smoothness for the engine as it is running with current equipment.

 

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