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lucid
Joined: 15 Jul 2008
Posts: 12
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 Posted: Tue Jul 15, 2008 7:42 pm Post subject: double base gasket on 85cc kit |
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when I bought 85cc cylinder and head I got two base gaskets with it.
my mechanic put both of them claiming that if only one base gasket is used
the valves are too close to the piston tdc 
I would like to remove one gasket because my compresion is low.
anybody with same problem?
is it possible to use only one base gasket (1mm) ?
what to do?
the cylinder kit is from taiwan. |
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Brighton Russell
Joined: 30 Jun 2008
Posts: 57
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Location: Brighton, England.
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| Posted: Tue Jul 15, 2008 7:59 pm Post subject: |
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| my kit also came with 2. and this was on the advise of the seller. when I fit mine I will use something to check the clearance, there is a putty like substance I cant remember its name. that you use. |
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JumpSteady555
Joined: 18 Aug 2007
Posts: 457
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Location: Pigeon Forge Tennessee
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| Posted: Wed Jul 16, 2008 12:21 am Post subject: |
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| Brighton Russell wrote: | | I will use something to check the clearance, there is a putty like substance I cant remember its name. |
Plastigauge, I used the stuff when I rebuilt a car motor in auto mechanics class.
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jpmacd733
Joined: 03 Jun 2007
Posts: 1529
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Location: Saginaw, MI, USA
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| Posted: Wed Jul 16, 2008 1:13 pm Post subject: Re: double base gasket on 85cc kit |
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| lucid wrote: | when I bought 85cc cylinder and head I got two base gaskets with it.
my mechanic put both of them claiming that if only one base gasket is used
the valves are too close to the piston tdc
I would like to remove one gasket because my compresion is low.
anybody with same problem?
is it possible to use only one base gasket (1mm) ?
what to do?
the cylinder kit is from taiwan. |
There has been a couple issues here where members electric start would not turn the engine over with the 85cc kits. At least in one case, a double base gasket solved the problem. The other never reported back on the results of a double base gasket.
What do you mean about compression being LOW. Have you measured it. While confirmation data is a bit sparse, it is my understanding that 120 psi for a new 50cc scoot is about right.
Joe
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If your not on two wheels, your wasting gas. |
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Brighton Russell
Joined: 30 Jun 2008
Posts: 57
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Location: Brighton, England.
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| Posted: Wed Jul 16, 2008 8:27 pm Post subject: |
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| JumpSteady555 wrote: | | Brighton Russell wrote: | | I will use something to check the clearance, there is a putty like substance I cant remember its name. |
Plastigauge, I used the stuff when I rebuilt a car motor in auto mechanics class. |
thats the stuff!  |
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Alexis050891
Joined: 23 Oct 2007
Posts: 232
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Location: Fife, Scotland Honda SA50J Met-In '90 only 3.2K on clock
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| Posted: Wed Jul 16, 2008 8:43 pm Post subject: |
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My 82cc kit came with one base gasket, but I had to make an extra paper gasket because the piston was hitting the valves. The kit still had enough power, at least it would start this time.
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lucid
Joined: 15 Jul 2008
Posts: 12
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| Posted: Thu Jul 17, 2008 5:14 am Post subject: Re: double base gasket on 85cc kit |
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| jpmacd733 wrote: | | lucid wrote: | when I bought 85cc cylinder and head I got two base gaskets with it.
my mechanic put both of them claiming that if only one base gasket is used
the valves are too close to the piston tdc
I would like to remove one gasket because my compresion is low.
anybody with same problem?
is it possible to use only one base gasket (1mm) ?
what to do?
the cylinder kit is from taiwan. |
There has been a couple issues here where members electric start would not turn the engine over with the 85cc kits. At least in one case, a double base gasket solved the problem. The other never reported back on the results of a double base gasket.
What do you mean about compression being LOW. Have you measured it. While confirmation data is a bit sparse, it is my understanding that 120 psi for a new 50cc scoot is about right.
Joe |
well ofcourse that the compression is lower than on the cylinder with only one base gasket because I have 85cc head also...
if I had the stock head and the 85cc cylinder the double base gasket would not make so much diference because the compression would still be high enough but with 85cc head too I lose
at least 1hp I think.
I know that the double base gasket is a must! with the stock head and cylinder above 50mm(82cc) |
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jpmacd733
Joined: 03 Jun 2007
Posts: 1529
Karma: +68
Location: Saginaw, MI, USA
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| Posted: Thu Jul 17, 2008 11:05 am Post subject: Re: double base gasket on 85cc kit |
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| lucid wrote: |
well ofcourse that the compression is lower than on the cylinder with only one base gasket because I have 85cc head also...
if I had the stock head and the 85cc cylinder the double base gasket would not make so much diference because the compression would still be high enough but with 85cc head too I lose
at least 1hp I think.
I know that the double base gasket is a must! with the stock head and cylinder above 50mm(82cc) |
Yes, the compression will be lower with double base gaskets. Your question was if you could remove one. For the most part, you answered your own question except for having the real number to make the decision. That is, the compression with the two gaskets. How low is it? If your compression is like 110 psi, then remove a gasket. If your about 125 psi then your near the stock compression and I would not change anything. If your planning to get the max out of the engine and run at 150 psi, then good luck. Get the real psi your at now and then you have something to base a decision on, or, just make a guess and go for it.
Joe
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lucid
Joined: 15 Jul 2008
Posts: 12
Karma: 0
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| Posted: Thu Jul 17, 2008 5:22 pm Post subject: Re: double base gasket on 85cc kit |
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| jpmacd733 wrote: | | lucid wrote: |
well ofcourse that the compression is lower than on the cylinder with only one base gasket because I have 85cc head also...
if I had the stock head and the 85cc cylinder the double base gasket would not make so much diference because the compression would still be high enough but with 85cc head too I lose
at least 1hp I think.
I know that the double base gasket is a must! with the stock head and cylinder above 50mm(82cc) |
Yes, the compression will be lower with double base gaskets. Your question was if you could remove one. For the most part, you answered your own question except for having the real number to make the decision. That is, the compression with the two gaskets. How low is it? If your compression is like 110 psi, then remove a gasket. If your about 125 psi then your near the stock compression and I would not change anything. If your planning to get the max out of the engine and run at 150 psi, then good luck. Get the real psi your at now and then you have something to base a decision on, or, just make a guess and go for it.
Joe |
I had the serial head and the 50mm(82cc) cylinder with two base gaskets and scooter ran much better than now with bigger 85cc head!
unfortunately the cranshaft failed after 3000km..why I dont know?
maybe from too big compresion or it
might be from my consistant usage od petroleum motor oil..who knows
true..I'm just gessing that the compression is really low now but its also true that my scooter was going much better with the stock head and I'm not really satisfied just because of that fact alone..
btw. I also bought many aftermarket parts for my agility but had no success so far
tried "ruima" race crankshaft,kitaco race coil,iridium sparkplug,bigger intake,softer spring and heavier and lighter rollers..no noticable gain of power except heavier rollers
the only thing I did not try is good brand name variator and exhaust..
maybe ill give one of them a try if removing one gasket fails
with the money that I spent so far in the scooter I could buy another one!
maybe I will if nothing works..
one more thing ..
my mechanic thinks it might work but hesitates...
the dealer who sold the cylinder to me says he has the same cylinder with only one 0,5mm base gasket installed (for races only though) and insures me that it can be installed with one standard 1 mm base gasket.
I'm aware that termo group(cylinder,head,crank.. etc..)would probably last longer with the current setup but I just need that extra 1-2hp that are just sitting there and waiting... |
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jpmacd733
Joined: 03 Jun 2007
Posts: 1529
Karma: +68
Location: Saginaw, MI, USA
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| Posted: Thu Jul 17, 2008 8:26 pm Post subject: |
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I can understand your mechanic being hesitant, he does not want to share the responsibility just in case the valves hit the piston. Nor do I. 
I would make the decision based on the current compression but it seems that you are not satisfied the way it is and have information that it should work without valves hitting the piston. So, just go for it. 
I am interested in what performance you are getting and what other performance parts are installed. There have been a number of posters that have been disappointed with a big bore kit. They noted improved acceleration but no increase in top speed. Most of those continued to use the stock CDI. Have you replaced the CDI with an unlimited rev unit? If so, do you have a tack installed and what kind of revs do you reach?
I would be surprised if you needed lighter rollers with the big bore kit. I guess you confirmed that.
There are not a lot of success stories about tuning a 50 cc scoot around here. Hope you have one for us.
Joe
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lucid
Joined: 15 Jul 2008
Posts: 12
Karma: 0
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| Posted: Fri Jul 18, 2008 7:58 pm Post subject: |
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| jpmacd733 wrote: | I can understand your mechanic being hesitant, he does not want to share the responsibility just in case the valves hit the piston. Nor do I.
I would make the decision based on the current compression but it seems that you are not satisfied the way it is and have information that it should work without valves hitting the piston. So, just go for it.
I am interested in what performance you are getting and what other performance parts are installed. There have been a number of posters that have been disappointed with a big bore kit. They noted improved acceleration but no increase in top speed. Most of those continued to use the stock CDI. Have you replaced the CDI with an unlimited rev unit? If so, do you have a tack installed and what kind of revs do you reach?
I would be surprised if you needed lighter rollers with the big bore kit. I guess you confirmed that.
There are not a lot of success stories about tuning a 50 cc scoot around here. Hope you have one for us.
Joe |
I have derestricted the CDI by my self and now it revs up to 9000,before it just started to kick in on about 8000 rpm
I cant say that I am unhappy..I'm happy because the acceleration is about 100% better but not happy because my scooter went way better with stock head and just the big bore cylinder..
unfortunatly the top speed didnt increase on either setup but thats because of the transmision..
the top speed is always 80kmh(50mph) weather I'm going downhill or on straight road...
I'm also not happy with aftermarket parts I bought..(cost/benefit )
I wouldnt be suprised if the stock camshaft performs better than the aftermarket one on my big bore ..I havent tried it unforutunately jet but I will when removing the gasket and I will post here..
overall I must say that I'm happy just because I can move normaly in city trafic now and before I couldnt because someone was always on the horn and on my taillight..
fuel consumption did increase betwean 0,5 and 1 liter but is still somwhere in the range of 3 liters on 100km. |
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Brighton Russell
Joined: 30 Jun 2008
Posts: 57
Karma: 0
Location: Brighton, England.
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| Posted: Fri Jul 18, 2008 8:06 pm Post subject: |
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| I fitted my 82cc kit today using 2 base gaskets as my seller advised. looks like I,ll need a new/bigger amp hour battery. as mine was not good on the 49cc but has no chance against 82cc!. its quite hard to kick over too. I put the high lift cam in too, that came for free. had a break in run on it and, whoa! how much power!. will have to up the main jet, (currently an 85) I think. but cant wait for it too free off a bit. will test it on the currently 24mph hill over the weekend, after an oil change. will post findings soon, but all looks good at the mo. only 2 hours start to finish too . |
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lucid
Joined: 15 Jul 2008
Posts: 12
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| Posted: Fri Jul 18, 2008 10:21 pm Post subject: |
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| Brighton Russell wrote: | | I fitted my 82cc kit today using 2 base gaskets as my seller advised. looks like I,ll need a new/bigger amp hour battery. as mine was not good on the 49cc but has no chance against 82cc!. its quite hard to kick over too. I put the high lift cam in too, that came for free. had a break in run on it and, whoa! how much power!. will have to up the main jet, (currently an 85) I think. but cant wait for it too free off a bit. will test it on the currently 24mph hill over the weekend, after an oil change. will post findings soon, but all looks good at the mo. only 2 hours start to finish too . |
"its quite hard to kick over too"
think that is because of bigger compression
your crankshaft may suffer..
my 82cc setup with stock head lasted 3000km and than the crank bearing failed..
I also had to change the battery with stock head |
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Brighton Russell
Joined: 30 Jun 2008
Posts: 57
Karma: 0
Location: Brighton, England.
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| Posted: Wed Jul 23, 2008 9:08 pm Post subject: |
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| the 24 mph hill is now a 34mph hill, so no holding up the traffic. 48mph on the flat. playing with jets/rollers at the mo. but I must say its the best performance upgrade for the money, that I have seen on any vehicle. and that includes all types. (I'm an oldie. 45!) |
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Fox
Joined: 05 Jan 2007
Posts: 5207
Karma: +244
Location: Los Angeles .... JmStar Sport 50.
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| Posted: Wed Jul 23, 2008 9:15 pm Post subject: |
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| Nice Job! It'll probably loosen up a little after some break-in. Use regular oil until a few hundred miles/Chinometers Then switch to synthetic. |
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