What gas with TL and 35cc domes (150psi)

[jjchambers]

So I picked up PabloEscobar's 95 SJ yesterday :woot:
It's got an ADA head w/ 35cc domes, analog TL, advanced 28deg, B-pipe, prop, single carb, etc...

Looking at ADA's website, it says 35cc domes should give me 185 psi... is their site wrong? Pablo says compression in his is 150. I don't doubt him at all.
link: http://www.adaracing.com/personal-watercraft/dome-yamaha-701/ya21

He's also been running 93 octane, is that necessary w/ the advanced timing of the TL and only 150psi? I'd like to get the compression up to 170 or 180 but will that require anything higher than 93 octane w/ this TL setup? I guess I want to know if advancing the timing requires higher octane gas?

Thanks!

Jeremiah

 

[Etheraldreamer]

that is weird. stock stroke? my stock stroke 61x with the same head and domes is sitting at around 182/183...
the t/l wouldnt change anything with the compression, so thats not the culprit. i would get a compression gauge and check it myself. and if it does indeed come up so low i would pull the head and double check the sizes on them. that seems very low for 35cc domes.

 

[jjchambers]

I will check the domes out tonight. I realize TL won't effect compression numbers but would it effect what octane gas I run w/ the advanced timing and all...

J

 

[OCD Solutions]

I agree, 34cc should give you 175-185.

I found cheap compression gauges to always give mediocre readings,even brand new. Just low enough to be believable and really mess with a guy. Usually 20-25lbs low. I finally bought a Snap-on set and haven't looked back.

Anytime I get a low reading, I always try another gauge for a second opinion before I get too excited.

 

[BombThreat]

Same thing as these guys are sayin, get a good compression tester and see what ya get... if its really 150 with 35cc domes then you should really think about freshing up your topend. Also your got 28 degress static timing but what are the modules (chips) on the system? You'll have three, one for the start RPM, retard rate, and a high rpm.

 

[Waternut]

I've seen Pablo's compression tester and he was using the same type of extension I was using when I got 10-15 psi lower than what it should be. I just think his compression tester is off. Most of us just use a cheap compression tester to make nothing is taking a dump. Try a reputable tester before you start thinking it's the engine.

My ski is around 170 with 35cc domes and if I put on the same extension, I get around 155.

 

[jjchambers]

Well I got the head off and they are 35cc domes, they have "YA2135L" scribed on them. Now to put it all back together and test it w/ another compression tester.
1) What loctite should I use on the head bolts?
2) What's the torque spec for these bolts?
3) Is there a torque rating for the spark plugs?

Here's some pics so you guys can check out the insides. Is this a little rich or just right? Cylinder walls look OK, no scratches or anything. Do you think I'll be OK re-using the o-rings? Plugs looked good on the darker tan side.

here are the pics!

J

 

[jjchambers]

Same thing as these guys are sayin, get a good compression tester and see what ya get... if its really 150 with 35cc domes then you should really think about freshing up your topend. Also your got 28 degress static timing but what are the modules (chips) on the system? You'll have three, one for the start RPM, retard rate, and a high rpm.

None of this effects compression right? You want to know b/c it would effect what octane gas I use, correct?

Jeremiah

 

[McDog]

That was my el cheapo compression tester he used. I think I got it at pep boys.

 

[Ryan_G]

If the cylinder is ported it will effect compression. On a ported cylinder I run 33cc domes to get 180psi. I couldn't really tell by the pics but it looks like the transfer ports were cleaned up. Get a good guage. Craftsman makes an affordable option.

1. No loctite, use anti-seize
2. First round - 15 lbs / second round - 18 lbs (Some would say not too, but I always give it a few more lbs on the final torquing) Start with the center bolts and work your way out.
3. I have no idea, Just don't over tighten it.

Your piston wash gives the impression your engine is running a little lean. If you really want to go tuning the carb you better start reading!

I say put that thing back together and go ride it!!!! Quit messing with it or it is going to be a never ending tinker.

Reusing the orings depends on their condition. Use supreme pump gas, whatever you have locally.(91,92,93)

 

[750SX]

nothing on the head bolts

 

[jjchambers]

If the cylinder is ported it will effect compression. On a ported cylinder I run 33cc domes to get 180psi. I couldn't really tell by the pics but it looks like the transfer ports were cleaned up. Get a good guage. Craftsman makes an affordable option.

1. No loctite, use anti-seize
2. First round - 15 lbs / second round - 18 lbs (Some would say not too, but I always give it a few more lbs on the final torquing) Start with the center bolts and work your way out.
3. I have no idea, Just don't over tighten it.

Your piston wash gives the impression your engine is running a little lean. If you really want to go tuning the carb you better start reading!

I say put that thing back together and go ride it!!!! Quit messing with it or it is going to be a never ending tinker.

Reusing the orings depends on their condition. Use supreme pump gas, whatever you have locally.(91,92,93)

No porting. If it is, then it's news to me and Pablo. I won't be able to ride until this weekend so I got new o-rings on order just to be safe. Thanks for the torque specs.

J

 

[701superjet]

if your running in salt water grease on every bolt, nut, electrical connection, just about anything

 

[BombThreat]

None of this effects compression right? You want to know b/c it would effect what octane gas I use, correct?

Jeremiah

that is correct, also is that salt corrosion on the deck of the cylinder? if so get that all scrapped off and cleaned with some solvent. i would also get those o-rings off and check them thoroughly. At least wipe those clean as well and re-install with a light coating of grease to keep them in place.

 

[Pablo]

that is correct, also is that salt corrosion on the deck of the cylinder? if so get that all scrapped off and cleaned with some solvent. i would also get those o-rings off and check them thoroughly. At least wipe those clean as well and re-install with a light coating of grease to keep them in place.

I cleaned the cylinder jackets with muriatic acid when i tore it down last winter. The ski has not seen salt water since I bought it in 07.

That piston wash does look as though it's been running lean. I'd go to 50:1 instead of the 40:1 I was running. The golden brown color on the plugs is what you're shooting for, but the piston wash tells another story.

 

[BombThreat]

I was just concerned mainly with the white spots on the deck and orings... its corrosion from something.

 

[jjchambers]

if your running in salt water grease on every bolt, nut, electrical connection, just about anything

What type of grease are you talking about? I was going to put anti-seize on the bolts and dielectric grease on the electrical connections, is that good or is there something else? Got new o-rings on order so I'll replace them for my piece of mind. I'll also make sure the mating surface is good and clean.

 

[jjchambers]

That piston wash does look as though it's been running lean. I'd go to 50:1 instead of the 40:1 I was running. The golden brown color on the plugs is what you're shooting for, but the piston wash tells another story.

Is that right? I'm try to figure this out in my mind. Is that 40 parts gas to 1 part oil. So I want to richen the gas mixture so more gas and less oil in the ratio, so it burns more and leaves less oil residue on the piston head... Couldn't I also adjust the HS or LS screws... which way would I turn them?

I'm kinda rambling and figuring this out in my head. So where's the mikuni carb tuning 101 manual?? I need something to read at work tomorrow.

J

 

[Pablo]

I was just concerned mainly with the white spots on the deck and orings... its corrosion from something.

Bombadier...no worries. The waterjackets did have quite a bit of corrosion when I tore it down last winter. I did hit it pretty hard with muriatic acid, but the corrosion caused some pitting. I can't recall if the deck was scored from the corrosion, but by the looks it must have been. I don't remember it being so bad that I was worried about it. JJ, since the head is off you might as well clean off that deck corrosion. I used anti-seize lubricant on the o-rings when I installed them.

 

[Pablo]

Is that right? I'm try to figure this out in my mind. Is that 40 parts gas to 1 part oil. So I want to richen the gas mixture so more gas and less oil in the ratio, so it burns more and leaves less oil residue on the piston head... Couldn't I also adjust the HS or LS screws... which way would I turn them?

I'm kinda rambling and figuring this out in my head. So where's the mikuni carb tuning 101 manual?? I need something to read at work tomorrow.

J

I said that wrong...twice. I said 50:1, but meant to richen the mixture (30:1 not 50:1) or change the carb settings. Go to the Mikuni website with this link http://www.mikuni.com/fs-tuning_guide.html for carb setup info. Or, factory pipe has some decent baseline info for carb setup with their pipes (see page 3 on second document below). I used their recommended settings on that carb, but have altered a little here and there with the low speed, since the initial setup. Sorry for the confusion on the fuel mix ratio. I used the blue loctite knock-off brand, from Northern tools, on all the engine bolts.