Help me identify this cylinder's strengths

[Zero Client]

Hey guys,

I've got a 62T-Y1 717cc cylinder that I don't know whats up or what it was meant for. I took it out of a '94 WaveRaider, but the cylinder's objective has got me stumped. Ive re-built it twice as I just can't get the squish dialed in correctly for my WB1 application. At 0.045" squish and 170psi there were still signs of pre-ignition on the pistons and ADA-head domes with pump gas. I was running a 0.050" base gasket too and it still needed more squish relief.

It's possible this cylinder was re-worked 10~15 years ago. Its also possible many people tried there 'magic' on it as well.
On the outside, its engraved RIVA on the front, and also 0645 on the back side.
Its been re-sleeved, likely by LA Sleeve
The cylinder had been bottom decked 0.010" - likely at the time of re-sleeve.
Its been ported. The port job looks pretty clean. I'm thinking maybe Riva did the port-work.

I have no clue if this Cyl is supposed to be running pump or race gas.

I have no way of accurately measuring the port widths, but heights from the cylinder top are as follows:
Top of Cylinder to:
Exhaust port: 35.75mm
Exhaust port total Height: 33.3mm

Top of Cylinder to:
Intake and Boost ports: 53.3mm
Intake heights: 16mm
Boost port height 22.5mm


My engine builder took one measurement - to the top of the exhaust port - and said I need to ditch this cylinder and get a 61x. He also mentioned that the setup may have been planned originally as a stroker motor. The engine cases are stock 62t no porting.

Thoughts?

 

[McDog]

Listen. to. your. engine. builder.

 

[Tyler Zane]

Listen. to. your. engine. builder.

Na, what do they know..

 

[Blue]

Typical 62T cyl exhaust port top measurment is 38mm so yours has been raised allot. This is typical in race porting specs. 170 psi does not require race gas typically but WB1 riders tend to run wide open for longer periods of time requiring less timing or more fuel to keep it from causing pre ignition. Depending on ur carb set up you can either go up a jet size or try opening up your high speed screw 1/4 turn. Do you know what jetting your running??

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[Nuklear6]

Your cylinder is consistent with most of the old Riva "race"/go fast engines I've seen come across my bench. After you subtract the .75mm negative deck height you have from the port measurements you took your exhaust opens at 83.8 deg atdc (192.4 deg duration), intake opens at 115.5 deg atdc (129 deg duration). These are all pretty good numbers for a blaster to run around (let's be honest there is no chance of a flat water flip so why not go fast on the top).
Your running a base gasket about double the thickness of stock to make cylinder height work with the standard Ada domes (I'm assuming) which have a squish step of .015". this tells me more then just the .010" you say was machined off the bottom was taken off the top. to run wide open with your port timing and a blaster (which loads an engine much harder then a stand up) I'd love to see you open the squish up to say .055" instead of the .045" you have. I would do this by machining the squish relief in the domes instead of spacing the cylinder up any further and raising port timing even more.

As far as detonation: verify static ignition timing is in the stock position, increase squish clearance and then richen up the top end (as others said)

Hope this helps

Chuck Palmucci
CPT Enterprise LLC
609 510 3062

 

[Zero Client]

Blue / Nuklear,

Thanks a bunch for honest responses. I'm running dual OEM SBN44s off a GP760. Jetting specs:
Pilot - 122.5
NS - 2.0
Spring - 65g (I tried 95, and then 80g, but the 65g worked noticeably the BEST just off idle)
Main - 115~125 (Still dialing it in)

Current jetting the ski hits actually VERY well down-low - even given the exhaust port heights AND the 050" base gasket. I'm excited to see how it might run with a 015" base gasket with 0.055" squish...


Wouldn't I need about 40cc ADA domes to start, given that lowering the cyl/raising the piston ~1.2mm equals almost 6cc of volume? I'd then have the 40cc domes cut with 0.045" relief. Aiming for 170~190psi pump gas.

Would this rock a WB1?

 

[Blue]

Glad to help. Yes It would make it better on the bottom since you would be lowering port timing. You would probably need 40cc or 42cc domes to modify and end up at your goal of 170 to 190 psi if your going to a thinner base gasket.

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[TheBuzzard]

I always say, DONT TRY AND TURN SOMETHING INTO SOMETHING ITS NOT. my first RN was mike coe's world finals winning race ski. the thing had huge exhaust ports raised to the moon, 3 base gaskets and decked on top .040 squish 210 psi. I wanted more bottom end for rolls so I lowered the cyl, cut different domes and even took out the 140 mag pump and put a lower pitch prop.it made an insignificant difference, not worth the work. I even tried a longer B pipe chamber since it had a modified mod on there. it still had 205 compression and .040 squish. if I ever want a race motor i'll just put it back the way it was, cause it'll never be a freestyle motor. if you change things on your motor, i'll bet you wont be pleased with the results.

 

[Zero Client]

So I put this turd back together with a .010" base gasket and a .050" head gasket. Squish is sitting right about at 0.055" now. Compression is 165psi with 35cc domes.

So if this turd doesn't suck and works I'll be looking to trade these 35cc domes for 33s or 34s.

Thanks guys!

 

[Zero Client]

LOL! So, with the cyl dropped and the squish at .055", the engine was sucking in more air and was asking to be richened. I went from 122.5 > 125 > 127.5 pilot jets and each time got better down low! No bogging, and no hesitation. Dropping the Cyl like I did really woke it up a bit. I'd say this engine setup is working absolutely perfect in the WB1. Its best power band is from 1/3 to 2/3 throttle which is great for corner exits and mid-speed wave jumping!

Thanks for the help guys!