Andyb1987 Posted March 26, 2018 Report Share Posted March 26, 2018 Hi again all I have a '99 montesa 315r currently having pinking issues what size base gaskets are people running I have a .5mm on at the minute and its driving me crazy also have a 46 pilot jet and a 120 main jet I read alot about people fitting a thicker base gasket and even fitting 2 but what size. There are .3 .5 .75 1.0 any advice is greatly appreciated. Quote Link to comment Share on other sites More sharing options...
section swept Posted March 26, 2018 Report Share Posted March 26, 2018 (edited) Your engine may be drawing air from the crankshaft bearing seals, this weakens the mixture and of course crankcase compression will be escaping to. Thicker base gasket will raise barrel a tad thus lowering compression a little and port timing will be altered very slightly. Playing about with the base gaskets will give you a softer or peppier engine. You may need to remove excess carbon from cylinder head, assuming it is pinking you are hearing and not something else. Pinking is another term used to describe detonation in the combustion process, an example would be the fuel and air mix being ignited but the remaining fuel and air explode creating extreme pressure on the top of the piston...obviously not good. Some tuners set an engine up so that it is just on the verge of ‘pinking’ and then adjust ignition accordingly.....this is sometimes when an engine might let go (bang) and it’s when the tuners sphincter muscles tense up? If you can, have a look at the crank seals, sometimes tell tale oil is visible indicating that they are worn. Hope you sort the issue ok? Bike looks to be well cared for? Edited March 26, 2018 by section swept Quote Link to comment Share on other sites More sharing options...
Andyb1987 Posted March 26, 2018 Author Report Share Posted March 26, 2018 I have no issue with starting running or anything other than when I rev it and close the throttle I get a rattle on run down Quote Link to comment Share on other sites More sharing options...
gazza7965 Posted March 26, 2018 Report Share Posted March 26, 2018 These bikes do seem to suffer badly from pre-ignition or "pinking". You cannot retard the iginition as there is no movement on the stator. The only way I could get my 2002 to run to my satisfaction was to add a 1mm head spacer. This lowers the compression without upsetting the port timing with the addition of additional base gaskets. I tried to do it through carburation using differing size pilot jets and changing to a Keihin and different fuels and octane boosters but by far the biggest improvement was achieved with the head spacer. Pinking gone and no noticeable loss in power. 1 Quote Link to comment Share on other sites More sharing options...
Andyb1987 Posted March 26, 2018 Author Report Share Posted March 26, 2018 Gazza where can I get a 1mm head spacer from? Quote Link to comment Share on other sites More sharing options...
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