Valve Gap sizes

[BrettS]

Hey Jonesy
The engine was always cold, At first I seemed to be getting .02 under our measurements (even tighter) on the inlet sides so I was blaming my cheap feeler gauges or your worn ones  But then I started to notice inconsistencies on the day as well so I took things very slow. After I had distributed the shims as best I could calculate I went over all the clearances again. When it started getting silly I started turning the cam in different positions and found that a slight change on the rotation, always on the round half, made a difference.
When i found the inconsistency I took my time cleaning the gauges each time and gradually stepped up in size so I am pretty sure my readings were correct.

Took the bike out for a few rides today. It seems to be a little smotther down low 

[Jonesy]

Hey Brett
Did that differ much from our original figures? and
just out of curiosity did you start your shim check with a warm engine that got colder as you went along or was it a cold engine from the out set?

[BrettS]

I spent a fair time measuring and swapping and measuring again all the gap sizes yesterday. I found on some the gap was inconsistent depending on where in the round half of the lobe you measured. One changed so much it went from .19 to .30
Not sure if this means I need a couple of new camshafts or that can be a normal thing.

So considering this with triple checking and taking my best guess when it was inconsistent I now get.

Ex .21? .21? .24 .23  In .12 .19 .15 .12

I need another 255 shim to cut that .19 down to .14 but I think I can get away with this for now, considering earlier engines this is within range. The ? shows the two with the most inconsistent measurement. One of them just as it went to the rounded section got a reading of .30 but with the lobe pointing straight away from the shim I got the .21 reading. at some point I got the .19 reading.   

I just hope I have made things better. Raining here so I haven't gone for a ride but seems to run the same so far.

[petejw1966]

i read that too bretts,
that it should only be the later models
but the rh is basically a 78 model engine and i always kept
the intake clearances to 4-5 thou without any issues.

[BrettS]

I was about to pipe up that the valve clearence changed on the models after 1980 so check the engine model first.

Looked it up in the supplementry section of the manual and now I realise it is only the Intake valve clearence that is tighter DOH! So My exhaust clearence is still too tight dam.

The supplemt states for 1980 on the intake valve clearence should be 0.11-0.15 It just cuts down on noise apparently but should only be done on 1980 onwards.

So I guess if my exaust valves are not closing soon enough this could be where my fuel is escaping?

Here is my numbers at the moment (hope you don't mind Cooper?)

EX 0.9, 0.11, 0.14, 0.13     IN 0.15, 0.1, 0,11, 0.12

Better see what shims I have and order a couple more I think.

[petejw1966]

jat

when checking valve clearances i use imperial instead of metric,
every .5mm step up is a whisker over 2 thou,
inlet clearances depending on model would be 4 - 8 thou,
exhaust clearances 8 - 10 thou.

i just find it so much easier and u dont need any chart to check against,

as i said its jat.

[Cooper]

Thanks for link decided to order one thats very reasonable price Coops

[Fred]

Valve Shim tool $11.98 + post CLICK

You'll find them a lot on ebay for about that price with differing postage costs

[SCARFEY]

Backfiring up the carby....mixture to lean or the timing is out or both.
Backfiring in the muffler Timing is out and or it's dumping unburnt fuel into the muffler and it burns (bangs) there

Valves, valve timing or fuel.

[Cooper]

Thanks for reply yes it was just a  guide mainly 13 and 18 exact measurememts I will take proir to ordering slimmer shims. Im now  making Steptoes valve  adjuster, original valve compressor is still obtainable for $92 so I'll make one save a few dollars.Coops

[Fred]

Coops,

Highly!!!  unusual for all to read exactly the same but they should read:

Ex -   0.21 - 0.25

In -   0.16 - 0.20

so, yes they need a bit of a tweek.

As Jonesy pointed out these would not be the cause of the backfiring (is it a true backfire or just a popping noise caused by sucking in some air?)

[Jonesy]

looks like all of them could have 0.05mm thinner shim to be as the manual suggests for correct clearance. most likely not the cause of the backfiring but

[Cooper]

Hi everyone just recorded valve gaps and wondering if they are to small. I have noticed a slight backfiring [very minor rumble] when throttle backed off As the engine is running well and idles excellent here they are.

                   EX  1. 0.18            In 1   0.13
                         2  0.18                 2   0.13
                         3  0.18                 3   0.13
                         4  0.18                 4   0.13

Should I leave them or replace with new shims. Regards Coops