Enfield Bullet:Cam gear backlash and solutions including adjustable cam spindles

[deepclutch]

cam gear backlash is a very common thing with RE Bullets .According to many , Adjustable Cam gear Spindle when fitted properly can fix that "tak tak" sound.
New Bullets comes with adjustable cam spindles by default.

AnyBody can give some more info.last day I went to Coimbatore and bought Adjustable cam gear spindles(Rs170/- ).

Acc to experts ,there is no use of fitting adjustable cam spindles with worn out cam gear setup.new set of cam will cost around Rs1200/-.
Can we change only the defective part?
IS there any side effect(s) with cam gear back lash?

B.R Gurunandan also explains the need to change to these type of spindles.

Nandanmotors : Serial Index

[Sankar]

Ah i see that you're going against you'r mech's "engine poliyum" theory

[deepclutch]

^well ,I got more than a mechanic at my disposal.but how many mechanics I met ,even at coimbatore ,not even one guy is particular about adjustable spindles .(though they can).

@sankar: please if you know ,explain the cam gear setup of Bullet.How many gears? 3 nos? any pictures?

[Sankar]

Buy three new cogs and buy only OE part that comes in the RE packing. Three cogs are Inlet cam, exhaust cam and the crank pinion.

Nandan's article is good and very informative and helped me quite a bit during my initial Bullet days.

[deepclutch]

And will you explain How the adjustable cam spindle help stop the gear backlash?

and I hope below one's are what you explained before?

[kuttapan]

@deepclutch - What you call adjustable cam spindles are basically eccentric cam spindles. I hope you know what eccentric means. In the normal concentric spindle, even if you rotate the spindle on its axis, the cam would not move in a horizontal plane, but with an eccentric spindle, you are able to bring the cams together to reduce backlash. But as you rightly learnt, eccentric spindles are not a solution to fix worn cam gears, though you may getaway for a while by having a tight cams - it is detrimental for the engine in the long run. So to put it in a nutshell, eccentric spindles enable the cam gears in the exhaust and inlet cam to come closer(or further) so as to reduce backlash.

The problem is, even when you buy a cam set from RE, they may not match 100% due to the manufacturing tolerances. That's why you find even RE going in for adjustable spindles, instead of searching for matching cam gears from a pile of 1000. Experienced hands are able to rotate the cam gears against each other, listening closely to see if they match.

[deepclutch]

thanks kuttappan for clearing the things.I feel ,I will go for a set of new cam gear+adj spindle changed in RE brand store workshop ,Edappally .

Originally Posted by kuttapan

But as you rightly learnt, eccentric spindles are not a solution to fix worn cam gears, though you may getaway for a while by having a tight cams - it is detrimental for the engine in the long run. So to put it in a nutshell, eccentric spindles enable the cam gears in the exhaust and inlet cam to come closer(or further) so as to reduce backlash.

Your Explanation is so clear.I hope other Bull owners also benefit from this.
--
sorry for so many question ,kuttappan ,Sankar and other engine geeks?
Many of the mechanics claims they fix the backlash by using "bush" or oversize Spindle(which means drilling a bigger hole???).Any Idea whether such setup will harm engine?

[kuttapan]

Oversize spindle basically does the same thing. Bring the cam gears closer. But to get this right, you need to machine the spindle to exact specifications i.e you need to know how much the gears should come closer. Eccentric spindles let you do this in an easier way.

You need to drill a bigger hole, yes, and done right, there should be no issues with the engine. However, I would recommend the eccentric spindles anyday.

Maybe you can pick the brains of whoever is suggesting oversize spindle and tel us why they think it is better. There is always an opportunity to learn, you know.

[deepclutch]

most common solution is to fix a "bush" with spindle.this bush will anyways will finish out in matter of few 100 kms.

Now ,I inquired in Coimbatore ,regarding the cam gear set.They said 2 types are there.One being OEM RE made and another One without any company name.but second one is mostly taken by others.Which One do you recommend?Is there anything we need to check before buying cam gears?
--
OT:
and @kuttappan where are you from?

[kuttapan]

Bush on a spindle....Hmmm, then I would advise not to go that route.

OEM one costs 1000+, the other one is a fraction of the cost. I would recommend the RE one, though the other one may do the job equally well(Just hope that it does not wear out sooner).

Well, I do not think you will be able to check backlash before buying them, so just make sure they come in OE packing.

I hail from Kerala, in US at the moment.

[sureshkishore]

Dear Kuttappan,

Been using my bull since college days. I never had the tick-tick (cam wheel) noise on it. But, last time I had the cam cover removed to check the oil pump I noticed that the two Cam Wheels weren't OE, instead they had eccentric spindles. Not only that the two other wheels, #1(idler) that drives the #2 timing gear. Both were made of Nylon . Ever heard about those before? probably dad had them put in long back. because since I got the bike the cam cover was never opened.
Can you throw some light on these. Should I change them back to OE? As of now the gears look in good shape and the bike's performing ok too. Need advice.

[deepclutch]

Both were made of Nylon

??
you mean cam gear!

Now @kuttappan ,@sankar : Is it better ,if I buy the OE royal enfield cam gear set from coimbatore and give it to the RE brand store service centre? last I heard ,they dont have stocks of the same in their workshop.

[lurker]

Originally Posted by sureshkishore

Dear Kuttappan,

Been using my bull since college days. I never had the tick-tick (cam wheel) noise on it. But, last time I had the cam cover removed to check the oil pump I noticed that the two Cam Wheels weren't OE, instead they had eccentric spindles. Not only that the two other wheels, #1(idler) that drives the #2 timing gear. Both were made of Nylon . Ever heard about those before? probably dad had them put in long back. because since I got the bike the cam cover was never opened.
Can you throw some light on these. Should I change them back to OE? As of now the gears look in good shape and the bike's performing ok too. Need advice.

I am no Bullet nut nor an engine expert ..

but never change what ain't broken.

[Sankar]

Originally Posted by deepclutch

most common solution is to fix a "bush" with spindle.this bush will anyways will finish out in matter of few 100 kms.

Now ,I inquired in Coimbatore ,regarding the cam gear set.They said 2 types are there.One being OEM RE made and another One without any company name.but second one is mostly taken by others.Which One do you recommend?Is there anything we need to check before buying cam gears?

Buy only the OE cams, don't buy the unbranded stuff. OE is expensive that is why most of them take the other item.

The bush you say is fixed inside the cam gear. It's made of bronze and is press fitted inside the cam gear. This is done when the ID of the cam gear increase (or when the OD of the cam spindle decrease or both) due to wear and tear. The bushing if done properly is not at all bad.

But bushing and eccentric cam spindle are for solving two different issues.

Eccentric cam spindle is used to adjust the gap between the three main cogs; the crank pinion, exhaust cam and the inlet cam. Nandan's article explains quite nicely why some engine needs an eccentric cam spindle. If the three important cogs in your ride are not meshed properly, when pressure on the cogs increase as they open the valves against the pressure exerted by the valve springs, the teeth of the cogs will strike against each other as spring compresses and decompresses. If the cogs are meshed properly there is no clashing of the teeth as the spring loads them and unloads them.

With adjustable cam spindle first you have to mesh the exhaust cam properly with the timing pinion. Once that is set mesh the intake cam with the exhaust cam.

Well another added benefit with the adjustable cam spindle is that once the spindle wears out (the surface cogs run on) you have a choice to replace only the outer eccentric shell of the worn spindle with the shell of a new one you buy. No need to drive out the whole spindle from the crankcase and drive in another new one as in the case of a ordinary item.

[deepclutch]

thanks for the info @shankar.OE cam gear comes at around Rs1200/- AFAIK.RE brand store workshop(edappilly) is where ,I am hoping to give my bike to.will do after November 25th(am travelling elsewhere in between).

It is a real interesting stuff ,if sanker can write a howto on the need for adjustable cam spindle on CI engines.{If sanker got his time!} .
Thanks @kuttappan and @sanker and others .I will be updating this thread with the turnouts after changing cams and adjustable spindle.

and Do we need to have something like "running-in" after going for new cam gears and adjustable type spindle?