Shovelhead and primary belts - part deux of the story

[Nenad]

Yes, it's me again, posing another conundrum. This time about primary belt adjustment: slack, vertical, horizontal, sideways, you name it, it'll be covered here. Hopefully.

Let me begin by stating that I love primary belts. Having used them since '79, and only had to replace the belt once, in '96, I will NEVER even consider a chain. Smoother and quieter ride, more reliable, and not least getting rid of the ugly, bulky primary cases. After all, this is a chopper and the reason I initially fell in love with Harley engines (other than pulling the chicks, but that's obvious, innit?) is that they're narrow and aesthetically pleasing, and tweaked properly will outrun any Japanese bike – at least that's what we used to do in the 70s – 80s Less bulk, less weight, sleeker shape, sexy paint job, Jap-killer by any standards (OK, somewhat depending on fork extension in tight curves, but who'd be that picky, I ask you. Just gimme a stretch of straight motorway and the girl would be in ecstasy. Eh, you felt vibrations? Sorry, did you say that you've just come? No problems, compliments of the house…).

Getting back to business (and what I wrote to Primo about, but obviously they didn't feel compelled to answer):

I've been using what was initially a Phase III primary belt and pulleys, 1 1/2", with their racing clutch, since 1979. Doing nearly annual rebuilds/makeovers for the first ten years or so, I've never had any problem adjusting the original belt. And the only time it broke was in '96 (my first stint in M'sia), when I replaced it with a Primo belt. I also have the gearbox main shaft support bearing in place.

As I've recently done a full rebuild I've bought a new Primo belt, just in case. And this is where the problems started – actually with both the old and the new belts, I've tried them both so I know it's not a belt issue.

I just can't seem to adjust the gearbox (i.e. the clutch pulley) correctly. Initially, the belt(s) was slipping inward (toward the engine and gearbox) just kicking the bike over, so I've spent days doing adjustments to the gearbox. Right now, it stays straight when kicking over, and even when starting it. But as the revs increase, the belt starts slipping inward on the front, engine pulley. The rear pulley is fine, the belt stays where it should.

The only difference this time, compared to all the years that I've had trouble free belt adjustment, is that instead of a homemade (fairly crude) gearbox mounting plate, without any adjustment facilities, I've now installed a "state of the art" adjustable plate, with separate screws for the left and right sides. I certainly thought that this would be a piece of cake to adjust, considering that I used to do it previously just using my eyesight, adjusting the belt tension by first stretching the final drive chain and then inserting a hammer handle (I told you it was crude) between the right hand side of the gearbox and the mount and pulling back to get it more-or-less in line, while screwing down the gearbox nuts. And I've always assumed (as it's always performed faultlessly) that this is an extremely simple setup.

Would you have any tips on what's going wrong? For the first time in my life I've actually checked the "squareness" of the pulleys, both vertical (which is perfect, as far as I can see, using a long level), and horizontal. The second one is where I think the problem is. If I adjust the gearbox for near-perfect horizontal squareness, that's when the belt starts creeping inwards on both pulleys. And if I adjust the gearbox "clockwise" ever so slightly, the belt stays in place until the revs increase, which is when it starts moving inward on the front pulley only! (Because, I assume, it's not quite square with the rear pulley...) The belt runs against the rear pulley outer edge and approx. 1mm in from the front pulley edge, but that's what it's always done...

I did have the front engine mounts re-welded and strengthened (and machine cut flat afterwards, with both crank cases screwed together) during the rebuild, as I've had regular problems before with the front mounts cracking, but I haven't touched the mounting holes other than drilling through the welds and making sure they weren't enlarged/oval.

Surely I won't have to go back to the old homemade plate? At least that's what I'm hoping for!

Sorry for what may come across as verbal diarrhoea to some of you... I'm celebrating my theoretical resolution to a non-battery Shovelhead setup and am currently on my second g&t... actually my third but don't tell my wife...

[panhead_pete]

As an aside why are you cracking front motor mounts? Are you bolting in the engine correctly then shimming?

[Nenad]

If I knew, I wouldn't be doing it... But over the years, for each rebuild, I've discovered ever so tiny cracks in the front mounts. And would always check that there was no play between the frame and the mounts, front and rear. Always absolutely flat, so this time I had a workshop take down the front engine frame mount bracket by 5mm and add the same amount to the crank cases. Properly machined flat etc. Rear brackets are OK, as is the top bracket. So, once I get the belt adjusted and can actually drive the bike I'll report on the outcome. We'll see how it behaves this time. it may be stroked and modified enough, being more appropriate for the strip than street, but should still behave...

[Blackbetty]

Certainly sounds like a shim issue to me...

I had to use shims trans to plate as well as plate to frame to get it to sit square.

Motor required some too...

What are you shimming with?

I'd take another look at the way the motor is sitting in the frame. If engine mounts are cracking it's probably not shimmed correctly.

[bustedlifter]

I purchased an adjustable transmission mount like the one you hsve. I found there isn't enough wiggle room in the slots for the case studs.Couldn't get it to adjust correctly so I opened them up a bit, but I haven't tried it since I put the Primo motor plate on my scooter.

[buckman50]

By chance do you have a Shovel inner primary that you can bolt to the motor and trans to assure you are in alignment? If not, see if you can bum one as this can be super helpful...some questions for ya:

1) Are you using the 5th mount on the tranny to secure trans case to the frame?

2) What hardware are you using to lockdown the trans to the transplate? If only using nuts, try nylock, lockwasher and a thick washer that wont flex....overkill perhaps, but you'll know for sure that trans and trans plate are one unit.

3) Is your motor a big inch stroker motor (+88")??? If so, maybe consider running an inner motor plate to secure trans to motor..you may be dealing with a torque issue.

4) How tight is that primary belt...do you have a MINIMUM of 1/2" belt deflection, cold? When hot, what's your belt deflection? If its super tight, that's a problem...

5) as noted above, is your trans plate to frame as well as your trans to to trans plate properly shimmed? Ive yet to have a trans plate to frame sit square without some amount of shimming needed.

6) Did you attach your drive chain to trans sprocket BEFORE bolting down your tranny? If so, and the chain is even a little bit tight, it will cause your trans case to sit proud of the trans plate, particularly the front side of the trans.

[Nenad]

Thanks for all the suggestions guys, helpful as always. I believe I've managed to sort out the belt alignment today, with a couple of shims...

Regarding shimming in general, I've always seen it as the last resort of the lazy mechanic , but maybe I've just been lucky all these years.

As for the engine mounts, both frame and crankcase, and following welding on extra 5mm of Al to the bottom of the front ones (to hopefully prevent future cracking), then machining both the crankcases and the frame, the engine once again sits squarely in the frame, with full seating between the two and with absolutely no play, not even the thinnest feeler gauge getting in anywhere. Considering the fairly large contact areas between engine and frame, both the one at the back and the two in front, I'm a confirmed believer in having full contact throughout. Unless one has very precise machined shims following the full mounts shape (which I've never come across), I just wouldn't feel comfortable using what are essentially thin washers and thus allowing a sizeable area of the mounts to 'hang in the air'.

As for the gearbox mount plate, although not at all happy about it, I can accept shims (mainly because I'm fed up with trying everything else and just want to get the bike on the road). Have shimmed the right hand side today, approx. 1.10mm at the back and 0.85mm at the front, with an additional fat copper washer (allowing me to squash it to the right thickness) between the gearbox and the fifth mount. So hopefully that's now sorted out. But am still pi***ed of that the fairly expensive, machined plate should need it, whereas with my old plate, hand made (but without adjusting features), I've never needed shims!

So, to answer your questions:

@Blackbetty:

The engine has always been sitting absolutely square in the frame, with no need for shims (see above) and I have no clue why the front mounts are regularly cracked. Hopefully with the extra thickness it won't happen again.

@bustedlifter:

My sentiments exactly. When I installed it initially, it positioned the gearbox ever so slightly anti-clockwise and the belt wanted to slip off towards the engine/gearbox. I resolved it by enlarging (by 0.75-0.8mm) three of the frame mounting holes, leaving the rear/left as it was. That finally allowed me to get the gearbox pulley square with the engine one. But it was still obviously out vertically, thus the last-resort shimming...

@buckman50:

No, don't have access to a primary, but am pretty sure that it wouldn't work as the engine mounts have been reworked (see above). As for your questions:

1. 'Course I am, have always used it.

2. The guys in the workshop have been laughing about this, but I've learned the lesson the hard way. So for the past 30+ years I've always used both lockwashers, nylock and permanent Loctite. On everything!

3. No, it's only got the 'mild' S&S stroker kit, 84" I believe, but with very hi-comp pistons (thank god they've recently introduced 100 RON here in Malaysia, no more mixing in alcohol with the petrol to stop detonations) and Andrews B cam (and a lot of other goodies), it used to be a 'Jap superbike killer'. However, I've never had any issues with things 'moving' before, maybe because of 2.

4. Having run with a primary belt for 37 years without issues, I do know to give it some slack. Normally somewhere between 3/4" and 7/8" total up&down play when cold.

5. Maybe, if I in the end don't decide to use my old, home made plate, I'll send it to you... Which has NEVER needed shimming... And the chrome is still good

6. Yes, the chain was on, but very loosely. And as I wrote initially, that's how I used to adjust the belt with the home made mount initially, without any problems...

So here I am, theoretically having resolved both the ignition (non-battery) and the belt alignment issues. Yet now the bitch refuses to start. Without any changes being made over the last two weeks. She's started to vomit petrol out of the air filter, 'coughs' on occasion, pretending to be willing but no cigar. Will have to check the pushrod adjustments, just in case the head gaskets have 'settled in' by now, as well as the ignition timing, once again. Although two weeks ago, with only the non-battery and belt alignment problems left (or so I thought), she was starting and running as happily as one can expect of an initially flawed concept. But we still love them, don't we, for whichever unfathomable reason...

[buckman50]

Glad you got it sussed out...

I would take issue with your shimming idea though...its a lazy mechanic that doesn't check to assure that no shimming is necessary ;^)

Please go ahead and keep your old chrome plate...I have 2...all junk.

As for your non-starting issue, it helps to tighten the nut between the handlebars first....that's probably your main issue.

Good luck, dude...and ride safe.

[Nenad]

Originally Posted by buckman50

I would take issue with your shimming idea though...its a lazy mechanic that doesn't check to assure that no shimming is necessary ;^)

I may be lazy and a lot of other things but I've always made sure that all my bits (yes, all of them ) either fit tightly or have the right play as it may be. Last time I considered shims was when I rebuilt the rocker covers and discovered excessive rocker arm play. But in the end I re-machined the spacers instead and thus avoided any superfluous parts. Additional parts, to me, mean additional complexity and problems...

Originally Posted by buckman50

As for your non-starting issue, it helps to tighten the nut between the handlebars first....that's probably your main issue

You've lost me there, I'm afraid, unless my familiarity with American English metaphors is woefully inadequate If not, all my nuts are adequately secured and otherwise up-to-spec, regardless of location