single v double base gasket?

[spooly]

iv recently done a top end rebuild for the first time on my 07 300 . it had two base gaskets previously and iv replaced it with a single pretty slim gasket. . My question is do I need to change the jetting? ?

 

[Zman]

My initial response would be probably not unless you replaced two thick gaskets with one thin one, but you will know for sure as soon as you ride it.

 

[Rick]

iv recently done a top end rebuild for the first time on my 07 300 . it had two base gaskets previously and iv replaced it with a single pretty slim gasket. . My question is do I need to change the jetting? ?

The two gaskets were more than likely to adjust port window timing in with regards to the piston dome. Kinda of a custom deal so to speak.

If you were able to separate the gaskets with out tearing them, measure the thickness of each one. The parts manual shows I think 4 different base gasket thinkness. The difference is to move the cylinder up or down to taylor the piston dome with the port windows.

More or less will have an effect of bottom end / topend.....

If you like the way it ran before, then go back to the stacked gaskets, but it would be who of you to know the base line from the old owner.

As for the jetting, you'll have to ride it and see.....

 

[Jakobi]

Measure your squish.

By reducing the base gaskets you 1) vary the port timing, but 2) you also decrease the trapped volume - increase compression, and this also moves the piston closer to the head.

Too much compression increases heat and kills top end/over rev. You may need to add more fuel to keep things cool, which could leave to fat/rich conditions and loading up when going easy on the engine.

 

[spooly]

iv been out on the bike and the only thing iv noticed is if your just rolling slowly in like 2nd gear and hit the trottle there's a blank spot Wright at the bottom like the first rev..

 

[spooly]

I can make another gasket if needs be.. I'll measure the squish that way ill know for sure first I need to buy a micrometer. .

 

[Zman]

If it is already together, ride it and see if you like it. The change should be noticeable but will not be huge. One final thought, if the cylinder had a ridge from wear at the top you could be at risk of challenges / problems because the piston/rings will not be traveling further up the bore and into the ridge.

 

[spooly]

good point about the ridge, but the cylinder seemed good couldn't see any ridge at the time. .

 

[spooly]

im going to add another gasket.. bike just feels horrible after first race.. it must be a timing issue.. does the 07 300 come standard with 2 base gaskets if so what size are they???

 

[Zman]

RE the ridge - you need to feel for a ridge looking will not tell you what your finger can feel. Increasing the base gasket will not address your bog issue. Reducing your base gasket thickness might as well as jetting.

 

[spooly]

RE the ridge - you need to feel for a ridge looking will not tell you what your finger can feel. Increasing the base gasket will not address your bog issue. Reducing your base gasket thickness might as well as jetting.

if there is a ridge what then? re-bore $$$

 

[spooly]

RE the ridge - you need to feel for a ridge looking will not tell you what your finger can feel. Increasing the base gasket will not address your bog issue. Reducing your base gasket thickness might as well as jetting.

my plan is to return the cylinder to the same hight as previous. .or close as I can..I will also check more meticulously for a ridge on the cylinder (with my fingers crossed) ..if anyone could give me the thickness of the original gaskets it would be a good starting point and more than likely what was on it previously. .

 

[Zman]

If there is a ridge, you can do as you say and put it back to the way it was or you can have it have it diamond honed if it has a minor ridge to remove the ridge and true the cylinder.

 

[spooly]

If there is a ridge, you can do as you say and put it back to the way it was or you can have it have it diamond honed if it has a minor ridge to remove the ridge and true the cylinder.

Thanks man

 

[spooly]

i tried to measure squish with 1.5 solder and couldn't get a press on the solder.. I its obviously more than 1.5.. so without knowing the size of the old gaskets im guessing my new base gasket is bigger the the previous 2(double) gaskets.. so thats probably the main issue atm.. im going to buy stom gasket paper and cut out some new gaskets.

 

[(F5)]

Unlikely. Squish on a std bike will be over 1.5. Much over they are super loose. Problem is if you skim it to where it should be, say .9mm the com goes super too high.

Search on threads I've started to read about head profiling if interested.

 

[spooly]

Unlikely. Squish on a std bike will be over 1.5. Much over they are super loose. Problem is if you skim it to where it should be, say .9mm the com goes super too high.

Search on threads I've started to read about head profiling if interested.

my next move is a .15 gasket and check and clean reeds and see how she runs then. .I also check the squish again once that is done. She's going to the suspension specialist tommorrow for a full rebuild and set up so I won't be able to work on it for a while. .which is good because my head is done in for thinking about port timing, gaskets , tdc , squish, jetting and so on ..information overload! !

 

[Jakobi]

Stock squish generally ranges from 1.9mm-2.6mm (depending on setup). A bit embarrassing really, but the factory has to make sure they'll run on any old fuel across the globe.

If you just drop the gaskets down to close the squish compression will go through the roof.

You're only going to be guessing what stack was in there without measuring what you took out, but FWW my 2010 model had 1.3mm of gaskets (from memory) and 2.6mm squish. Loads of threads on the topic though and should be well documented if you have a search.

 

[lonetree]

on my 04 and both my 09 bikes (250 and a 300) base gaskets are actually 3 gaskets, with a total thickness of 1.3mm. this lines the top of the piston up with the bottom edge of exhaust port....
stock squish on all these bikes is 2.3mm-2.7 mm
i have had one head remachined, to achive a squish of 1.3mm and its perfect (it also had the combustion chamber dome reshaped to get compression right)
hope that helps ya.

 

[(F5)]

Stock squish generally ranges from 1.9mm-2.6mm (depending on setup). A bit embarrassing really, but the factory has to make sure they'll run on any old fuel across the globe.

If you just drop the gaskets down to close the squish compression will go through the roof.

.

Yes but.
Point one contradicts point 2. Factory fault not yours. You'd think they would make the head bigger so if they ever did get a longer rod and a taller piston that used the squish space up which is super unlikely. The engine would still blow as its now 19:1.