Mounting a timing wheel on a 750SF?

TeddyG

TeddyG

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Location
Portland Oregon
I want to use a degree wheel to check the piston timing w/ the crank, but the Motion Pro degree wheel mounting hole is only @1/8'' and the crank has a 24mm nut. Enlarging the degree wheel hole accurately may be difficult. Any tricks or work around for this?
 
A hole saw answers the first question. Do it with a piece of timber as backing, it's painful for the pocket, $70 tool including an Arbor for one use only.
 
Hi Teddy. I have a bunch of cardboard ones, different holes in the middle, for different bikes. Anyway, to my tip... stick them on using blutack, you can then rotate them a little bit to get them cock-on under your pointer. They won't move under engine rotation. Easy on, easy off.
 
Thanks guys, gluing the printed wheel on thin cardboard and carefully cutting a 1.75" hole in the center firmly mounted the wheel onto the spindle and the good news showed that the timing marks all align as they should. Unfortunately, these wear marks on the cylinder walls indicate honing or re-boring will be needed. I can feel the wear grooves w a finger but the piston bodies have minimal wear marks.

What is the correct method for accurately measuring the piston ring gap between the piston grooves? When the rings are fully seated into the grooves, it's difficult to fit any feeler gauge into them, and w the rings more relaxed, it seems like a sloppy fit
 

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I don’t want to be mistaken for an expert, but I can’t help thinking that if the bore damage was causing a dramatic loss of power then you would probably have noticed the blue smoke and also had trouble all over the rev range. Could be wrong, but I’d be keeping a lookout for other causes while you work through the problems you’ve found so far.
 
Point taken Andy,
I'm trying to eliminate the possible causes for the engine's lack of performance past 50-60 mph, and have exhausted everything else. The carbs have been totally rebuilt w/ new slides/cables/synched/all the timing checks out/coils checked/new battery and plug cables/new fuel lines and spigots/new pod air filters/valve clearances are good. The bike starts up instantly, holds a steady idle and revs freely w/ no stumbles, but struggles past 50 -60. Possibly lack of exhaust mid pipe but have gotten different opinions.
 
TeddyG said:
Point taken Andy,
I'm trying to eliminate the possible causes for the engine's lack of performance past 50-60 mph, and have exhausted everything else. The carbs have been totally rebuilt w/ new slides/cables/synched/all the timing checks out/coils checked/new battery and plug cables/new fuel lines and spigots/new pod air filters/valve clearances are good. The bike starts up instantly, holds a steady idle and revs freely w/ no stumbles, but struggles past 50 -60. Possibly lack of exhaust mid pipe but have gotten different opinions.
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Yes, you’ve done a lot and must be getting a little bit frustrated by now…
 
TeddyG said:
Point taken Andy,
I'm trying to eliminate the possible causes for the engine's lack of performance past 50-60 mph, and have exhausted everything else. The carbs have been totally rebuilt w/ new slides/cables/synched/all the timing checks out/coils checked/new battery and plug cables/new fuel lines and spigots/new pod air filters/valve clearances are good. The bike starts up instantly, holds a steady idle and revs freely w/ no stumbles, but struggles past 50 -60. Possibly lack of exhaust mid pipe but have gotten different opinions.
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Well I know nought and plenty well acquainted with 750's have commented on the various threads, but I am a little confused about the regular reference to 50 - 60 miles an hour (but forgive me if I have missed more info)
So I take it that in top gear it will only rev to around 3500 revs? What happens when you get to the 3500? Does it miss / fart / nothing??
Does it rev out easily to 6 or 7000+ in lower gears? Obviously it would do more than 50mph in some of the lower gears so can only assume it is limited in all gears?
Does it rev out cleanly to 6 or 7,000 revs when on it's stand without any load at all (I know you mention it revs freely but how far?).
If it runs fine but will only rev to a certain range with or without load sounds more like a dodgy advance which has of course been mentioned before.
But anyway, if it changes character when under load more specifics might help (well someone on here anyway;))
 
There's some printable files of degree disks in the library section here: https://laverdaforum.com/resources/degree-disc-markings-4c-a11-cams.100/history

The images are sized such that they'll be the same size as a CD when printed on A4 paper. Just cut it out and glue it to a CD. You may need to adjust the size of the centre hole in the CD, depending what your mounting system looks like.

They were made up for the Laverda triples and are marked up with the cam timing for A11 and 4C camshafts, but they degree graduations so you can use them on any bike. The degrees go from o to 360 in both directions, so they can be attached to either end of the crank regardless of engine rotation direction.

If you prefer a generic disk without the specific Laverda triple valve timing marked, I can upload one to the library. Actually, I may as well do that now ...

Just uploaded it. Here it is: https://laverdaforum.com/resources/timing-degree-disk.150/history

While they're not as large as commercially available degree disks, they're large enough to achieve an adequate accuracy for engine timing. You can measure to within 1° easily enough.
 
You could stick it on with blu tack - unless you’re hoping to view it with the engine running. Presumably you only need to check the marks on the pulley are correct or make your own marks?
Whoops I’ve just seen Haggis has already suggested this!
 
Hi Normski - no problem.

By the way, I find the blu tack does not move when the engine starts and revs - you have to use a goof number of gobs of it of course, but it holds the disc solidly, even when everything is warm. There is very low mass in the disc.
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I make my discs using cornflakes packets, 2 ply, stuck flat under a heavy book, with PVA. I find my crappy-disposable discs especially good for valve timing because I get my coloured pencils out and scribble all over them for very easily visualising durations. The key to accuracy is getting the centre hole cut neatly and concentrically of course.
 
Thanks Shajota,

The engine revs freelyon the low end and builds speed up to about 40-50 mph in top gear at @ 3500 RPM, and will gradually reach 60, but I can feel the motor petering out w/ very little acceleration, and is dangerous to ride on freeways w cars flying by- it just doesn't have any acceleration left and I don't want to force it. It probably will do 70 if given enough time and distance, but the motor feels like it's straining.

So for now I have a nice shiny vintage bike for riding on the side streets-
 

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Hi Teddy, I am still unclear if your bike revs freely to much higher revs with no load.
Regardless, it appears (to me) from your description that a balance pipe would be unlikely to fix the issue. A balance pipe may well affect mid range on some bikes but your description suggests this is not a mid range issue but a significant strangulation of the engine.
This (to me) points to something in the basic set up (or completely worn out!!)
I note carbs were rebuilt, did you use the same cables or put in any elbows that might reduce length of pull?
Do the slides retract all the way into the body of the carb?
Probably all been said and checked before, but just thought I'd throw it out there.
Anyway, you have it apart now, so can see what is worn and when putting back together ensure all good. Has to be something simple surely........
 
What air filter is on it, try it without. How is fuel flow, blocked tank tap filters This is so crazy. Try it without mufflers, clutching at straws.
 
thanks guys,
I installed new carb slides and cables and new fuel spigots and fuel lines,tank is clean inside. the only thing I didn,t do was ultrasonically cleaning carbs which I,ll try next but I used compressed air on passageways when rebuilding them. New DNA pod filters on or off gave no change and exhaust is newish Malcolm Cox. It revs freely at idle to 4-5 K rpm. probably combination of scored cylinders and carb issue which I will pursue-
 
You have checked that there's no binding of brakes front and rear? Both wheels spin freely? And with filters off and throttle on the stops fully open you can see that the slides have disappeared into the upper carb body? It's just a very very odd problem - my unfiltered SF1 was so seriously shagged inside, broken rings, huge ridges at the top of each cylinder, worn out valves - but it still carried me from Darwin to Perth at speed. Enough power to accelerate hard to 130-140 when the bulldust up in the north west got a bit deep and set up a bit of a weave :eek:
 
TeddyG said:
thanks guys,
I installed new carb slides and cables and new fuel spigots and fuel lines,tank is clean inside. the only thing I didn,t do was ultrasonically cleaning carbs which I,ll try next but I used compressed air on passageways when rebuilding them. New DNA pod filters on or off gave no change and exhaust is newish Malcolm Cox. It revs freely at idle to 4-5 K rpm. probably combination of scored cylinders and carb issue which I will pursue-
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"I installed new carb slides and cables"
So, (sorry to repeat myself) do the slides fully retract when you wind the throttle on? (IE - bottom of the slide at top of inlet tract at full throttle - easy to see now while carbs are off if still attached to throttle)
No more from me - I'm sure it will reveal itself soon......
 
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Shajota said:
"I installed new carb slides and cables"
So, do the slides fully retract when you wind the throttle on? (IE - bottom of the slide at top of inlet tract at full throttle - easy to see now while carbs are off if still attached to throttle)
No more from me - I'm sure it will reveal itself soon......
Click to expand...
Good idea, outside the box thinking, and fits the symptoms.
What’s the pool up to…? 😉
 
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