4L1/4L0 Base Gaskets.

[steven]

Hi,
Does anyone sell base gaskets in different thicknesses for adjusting the squish band?
I measured a standard base gasket and it is showing as 0.5 mm thick.
I have looked round the net, but don,t see anyone selling any for a 4L1/4L0, although I do see some in different thicknesses for other bikes.
Has anyone ever tried running without a base gaskets and just using
some kind of sealer in an attempt to get the squish band correct? I have not heard of, or seen this done, but was just wondering.

What should the correct STANDARD squish band be for a 4L0? I read that it should be 0.8-1.0mm for a 250 and 0.9-1.2mm for a 350.
Im not looking for any performance type squish figure, just the STANDARD one.
Im wondering how many of us actually check our squish band? from what I read, manufacturers deliberately set the squish band wide, due to the problems encountered achieving tolerances in engine components during production.
I have checked mine, and they are approx 1.8mm, which is obviously outside the 0.9-1.2mm figure. I also read that "a wide squish clearance will not matter too much, peak performance will not be reached, and detonation will not occur unless the bike is driven hard".........but who rides an LC anything but hard!
Thanks in advance,
Steven.

[ianr4863]

From my experience a " standard " engine will always be around 1.8mm for the reasons you say . Many tuners say that the magic happens with squish set at under 1mm . Fahron will reprofile a 250 head for you to suit a 350 with pretty good results .
Cant help with the base gasket Im afraid .

[bryan]

standard you will be looking at well over 2mm, mine was about 2.5mm and the YPVS engine was a little less but over 2mm.

[bare]

One can DIY a set of base gaskets an easy task actually. But it can be tricky to source very thin gasket material.
Bigger and more relevant issue is the 4LO Head gasket is laughably too thick. I'd concentrate efforts on either deleting the head gasket or finding one that is similar or less thickness than the Valvie ones. Which are 3 layers of metal and are often separated to reduce their thickness for squish purposes. Sometimes aftermarket 4lo head gaskets are also of 3 layer metal (rather than the oem pressed together composite). A good choice. IF you can in fact find one?
Reducing the Squish , at least from the silly large oem 4lo setup, will let your engine run cooler as well as more efficiently. More benefits than merely 'go faster'.
So don't be too easily discounting it.

[bryan]

The chances are that all the fuel/air mix in the squish will not get burnt b4 the piston is past tdc, so narrowing your squich and getting that mix into the domes, where it gets burnt, is the point of reducing the squish.
Even if you have the head machined to keep the compression the same, you would get performance gains, but having the domes machined for higher compresion would gain you more. This could have been done by Yamaha, or any other manufactuer in production, but would cost money, so the tollerences are wide as its cheaper for them to manufactur them like that.
Its all linked to the tollerences of rod lenth, piston height, barrel lenth and head machining.
Get the job done properly, have a head machined and get a thinner head gasket or split a Genuine Yam one.
Thinner base gaskets will lower you ports also.

[steven]

Hi, thanks very much for the replies,
cheers,
steven.