Project Cafe Rocket 686 begins. Finally!

[Srinath]

So would it be better to run it on 87 octane ?
That means I should stay with 10:1 or under compression ?

I found a lovely cast piston (which I wholly prefer over forged) in 102. Whooo hooo ...

Thanks.
Srinath.

[zippy49]

So would it be better to run it on 87 octane ?
That means I should stay with 10:1 or under compression ?

I found a lovely cast piston (which I wholly prefer over forged) in 102. Whooo hooo ...

Thanks.
Srinath.

Please forgive me for jumping in here....but 87 Octane? Sounds like a recipe for disaster, even at 10:1. You'll want to measure the combustion chamber volume to check the actual C.R. I have a JE in my Velocette Venom, it is forged and fitted with Total Seal rings. Best piston I've ever used, and I've been through a bunch in that bike (had it since 1970!). A forged piston needs a bit more clearance, but it's much stronger and that's what I'd want in my Skorp. The ringset has a two piece 'gapless' second ring, too.

Since I live only a couple of hours away, I like APE for valve work. They have a Serdi full-radius cutter and made my XR650 run like a champ. Reasonably priced, too.

[edfmaniac]

Agreed. I run the highest octane I can get at the pump, 92 or 93 I think. If I had to build my engine again, I'd let the guy who did my head work make my piston. http://www.kenzcycletech.com/

[Srinath]

I guess even @ 10:1 I should run 92-93. OK.
I also should keep it indoors, cos it has the habit of taking in water from the cap.

There is a lot of engine shops around here compared to anything in most any other part of the world. I moved from Northern CA, and was amazed at how easily I could get heads done with 3 angle jobs or anything else I chose ... and cheap too. I paid 60 bucks 6 years ago to do a savage head (4 valve single) and have since then found shops that do better for less.

Has to be some advantage to living in "Left turn racing" country ... anyway this bike needs to live, and live for many many years and run like it did when it was stock ... I am staying with paper air filter and the supertrapp pipe ... no shooting for the moon here.
The 10:1 in forged and 92-93 will work ... thanks, I'll get those - my engine dude also is a big fan of forged pistons.

JE or wiseco ? any special preferences there ?
The Je is the one that was in there ... and busted ... Could stay with it, cos it cracked without destroying anything else ...

Cool.
Srinath.

[edfmaniac]

Have you measured your cylinder yet to see if it's going to work with whatever piston you choose? Just throwing another 102mm piston in there with new rings isn't going to last very long. You need a fresh hone on a cylinder that is bored to match your specific piston in order for the engine to last as long as possible. And you'll still need to check squish on the new cylinder too. Otherwise, I'd just buy a good used Yamaha Raptor cylinder on Ebay, buy the appropriate OEM replacement piston, and then take it to be bored and honed.

$95 - http://www.ebay.com/itm/Yamaha-Raptor-6 ... 1380265269
$70 - http://www.ebay.com/itm/YAMAHA-YFM660-6 ... 4897.l4275
$22 - http://www.boats.net/parts/detail/yamah ... 00-00.html

Just add gaskets and machine shop fees and you are almost there. I'd still consider putting on a new timing chain too while you are in there.

[edfmaniac]

And always run the best gas they have at the pump in your motorcycles. Just do it.

[Srinath]

The cylinder is supposedly in good condition. I am still waiting for final word on the size, but he said its not egg shaped, its not hour glassed. I am just waiting for measurements. If under 4.019 I'll get 102, else I am buying the cylinder piston set.

I am a creature of habit. I'll have to put a big sticker saying "93 octane only" etc etc on it. The GS and other bikes I own are jetted so rich, they dont care 87 works fine on them. This thing has been also taking in water. I need to keep it inside after that too.

Cool.
Srinath.

[DAVID THOMPSON]

TRY THIS LIST OF STATIONS

http://pure-gas.org/index.jsp?stateprov=NC

and get the ethanol out of your tank

your lawn mower and weed eater will run better on it also
dave

it cost a bit more but my rt 125 runs excellent on the stuff
the hard starting after it sets for a few days is gone.
it sat on the side walk out front all winter
put on a new fuel filter and drained the carb
and it started on the gas i put in the tank last October
the second time i cranked it over...

[Srinath]

There is no real reason why it wont run on ethanol and MTBE and what ever else laced fuel ...

Actually the thing is, while ethanol has its own oxygen and hence needs a lot more ethanol to properly burn into CO2 and water ... ethanol also is resistant to detonating and it burns slowly compared to Gasoline. In effect if we jet it, we will get it running right.

This bike essentially was detonated to death by me not knowing I had high compression pistons and not being able to keep it in the garage ... now I have room in the garage though, so it will live there, so will the other one.

Cool.
Srinath.

[zippy49]

Fuel varies a lot in how much anti-deposit additives are included. Makes a big difference in keeping the valves and combustion chamber clean. if you search "Top Tier fuels" you should find a list of companies that meet this standard. Costco is one, Arco/Valero is not.

MTBE has polluted many aquifers and waterways here in the USA. It is a toxic carcinogen. Ethanol, while a problem with long-term storage, is not all that poisonous (hic!) It does make our plastic fuel tanks expand, so I keep ours dry if not ridden regularly.

I once put a Wiseco piston in my XR650 motard. It was sold as and even marked "10.25:1" on the crown. When I finally checked the CR it was still stock at only 8.5:1!
So I prefer JE. And the Total Seal rings.

[Srinath]

OK JE and total seal ... I will work on getting those, I am fan of total seal too, and my mechanic has run em in his race car he said. Should be cool.
Cool.
Srinath.

[edfmaniac]

Make sure you measure EVERYTHING! The instructions are very specific about piston groove/ring clearances and cylinder honing. I suspect these rings are even more sensitive about being set up correctly since they do provide a near total seal. Here's the installation instructions if you haven't already looked at them. http://www.totalseal.com/TechPage.aspx# ... sPistRings Make double sure you have enough metal left on your cylinder for a fresh hone!

This quote's presence on their site makes me wonder how much better their product can be though, "I've been using Total Seal® rings in my engines for over 15 years. They’ve shown the most significant gains in power through improved cylinder sealing than any gains from cylinder heads or camshafts I've tried. Equally as important is the service and technical support I've received from their sales and tech staff." That's total bullsh!t in my opinion and a completely unnecessary statement. No racer in his right mind would give up his heads and cam for a slightly better ring seal. Traditional rings work just fine.

[edfmaniac]

And after reading a piece on valve stem blow by caused by the use of TS rings in a street motor, I see why they have the little piece on valve seals in their ring installation instructions. Have your seals checked or measure them for proper tolerance. Otherwise, you'll be adding to any oil consumption problems.

[Srinath]

I will ask my engine guy. I'll keep you guys posted. He's run them, I only heard about it and read about it.

How can there be valve seal blow by, the valves supposed to be open when its sucking, and supposed to be closed when compression ...
Can it squeeze past the seated valve ?

Yea 4 stroke the head is very important.

Cool.
Srinath.

[edfmaniac]

How can there be valve seal blow by, the valves supposed to be open when its sucking, and supposed to be closed when compression ...
Can it squeeze past the seated valve ?

Increased amplitude of crank case vacuum and pressure pulses would require a tighter tolerance in the seal to maintain the same blow by rate. It's probably not much, but the increase in oil usage should be somewhat relative to the increase in power unless you do something about the stock seals. Then again, I could be completely wrong. I'm just going by what I read too, but as a critic I chose to look at as many negative reviews as positive ones.