| Author | Message | ||
     Luisemilio25r |
I need help from experienced mechanics please. I'm in the process of adjusting my valves and my question is, how accurate should I be when measuring the gap? 1/10s mm or 1/100s mm or 1/1000 mm? I'm trying to figure out how many shims I need to get. | ||
| Luisemilio25r |
To be more exact, the difference between the shims I have installed with the ones the calculation sheet on the manual is indicating to install is .033 on some of the valves and .025 on others. Thanks! | ||
| Luisemilio25r |
Anyone?? | ||
| D_adams |
I don't have the conversion handy, but either shoot for the middle or loose side of the range of tolerance. Typically a higher revving engine will seat the valves some and reduce the clearance as it wears in. The chart is in the back of the service manual, you'll have to do some simple math to either convert it from inches to metric or just get close if you have metric feeler gauges. When I did mine, everything was tight and I was only able to re-use one shim. | ||
| Luisemilio25r |
I'm not talking about the conversion. I'm using mm for everything after all is a metric engine. What I wanted to know is how annal do I have to get in regards to the gap. How many tenths or hundredths or thousandths of a mm matter? | ||
| 1_mike |
As anal as YOU feel you need to be..! After all...it is YOUR engine. Despite the engines metric heritage, I live in America where most everything is still in inches. Including the Aerospace Industry where I work as a Test Engineer. So I did my measurements in .000" and did the conversion to metric to buy the shims I wanted. And as for the sought after finished clearance values, I went for the "top" of the range so I don't have to worry quite so much about having to do another valve adjustment in 6 months. As for any power increase or decrease in the top, middle or the lower range of the gap possibilities...not happenen... To get much of any h.p. difference with rocker gap, takes way more thAn just .002" or .003". This comes from years of tuning experience, not just a guess or one of the many engine wives tails or tuning myths. Mike (Message edited by 1_mike on September 22, 2010) | ||
| Luisemilio25r |
Ok mike. Didn't mean to offend anyone about the metric comment. But what I wanted to know is, would .001 inches would make a difference. | ||
| D_adams |
Only if it's on the tight side of the tolerance. That's why they give you a range of .004-.006" or .008-.010" to work with. (Message edited by d_adams on September 22, 2010) | ||
| Kicka666 |
Luisemilio25r are you talking about the valve clearance? All of mine were tight @ 4000kms. You say the manual is saying to use 0.33mm on some valves & 0.25mm on the other valves, thats sounds more like the specs for the valve clearances. For eg: if your inlets are tight say by .05mm & you remove a 2.80mm shim you would replace it with a 2.75mm shim to get the lash within spec, or smaller again if you want to run it on the loose side. A micrometer & a bit of basic maths & you cant go wrong. | ||
| Luisemilio25r |
Kicka, I already did all the measurements and calculations. I apologize I'm not explaining my self correctly. My questions is that if the desired shim is only .001 inches different than the installed shim, do I need to replace it or the difference is so little that it would be unnecessary to replace it? | ||
| Kicka666 |
If you want to get it spot-on, I sometimes take a little of the shim with an oil stone if I dont have the correct shim in stock, it is time consuming. If its still in spec its entirely up to you mate, if it was my bike I would shim them all to the upper side of the spec. As I did recently, I had to replace all but 1 of my shims & I had only done 4000kms. | ||
| Avc8130 |
If you set them to the tightest tolerance allowed you will maximize lift from your cam. I know guys that do small engine speed runs and they will adjust valves specifically to maximize hp. It might not matter on a 140hp 1125, but on a 125 every last itty bit matters. ac | ||
| Bigblock |
experience here online and from others I have talked to say they tend to tighten up over time, so better to set them in the middle or on the loose end of the scale. In my (admittedly small) experience, engines tend to make a bit more power with the valves a bit loose, for some reason I can't explain. Maximizing lift by tightening the valves is not always the best way to go for power. Now, I have no experience at all with 125's, and have not tried different settings on my 1125 to compare power or ET, or trap speed differences, so take it with a grain of salt... | ||
| Luisemilio25r |
thanks for your advice guys. I'm not really concerned about getting more power. It has plenty. I just want to make it as reliable as possible. I ended up buying 4 shims. Thanks again to all that awnsered! |
