Project Cafe Rocket 686 begins. Finally!

[pod35]

That is beautiful, quite inspiring. I hope to do something similar to my Tour and if it turns out half as well I would be v.chuffed. I'm on a very tight budget so I think it's going to take a few years but I'm ok with that.
Justin

[samandkimberly]

There are a lot of factors in setting up proper ignition timing. Compression, porting, cam work will usually increase burn rate, allow you to retard timing, but often the most efficient burn for a given motor will be with a lot of advance. Ideal advance in this case becomes limited primarily by pre ignition. I'd bet that Dynatek is working on the assumption that the rider can/will use race gas, and so they can run a lot of advance. More advance will make the bike respond much more crisply at lower throttle opening too, regardless of gas octane.

I'm somewhat in disagreement with Bill rgarding the suitability of the stock advance curve for street riding. yamaha designed that little dip in the stock curve to make a stable idle, a steep ramp to get to a decent advance for normal 3,500 RPM plus riding, and a gradual taper after that. All this is apropriate for a street bike, not necessary for a racer.

IMO, your best bet is to replicate the stock settings and, importantly, validate them by checking with a strobe. At a minimum, make an ignitech program that holds timing at 12 degrees and then see if the Yamaha timing mark stays steady when your check it with your light. Better yet, put some new marks on the flywheel and use them - my flywheel is marked in 10 degree increments so I can check timing accuracy over a range.

But stock, with a raised top RPM, will allow you to have safe fun and accurately compare the Ignitech to the stock ignition. Start messing with advance once your motor is broken in and you've got some time to play on the dyno.

Yep! Got it running but am still trying to get the Ignitech to perform as good as the stock box. I'm going to start over again with Bill's recommended curve and then just slowly increase the advance until I feel like it's performing as well as the stock box but with a cut off around 9k. What I don't understand is how much advance Dynatek uses on their Rhino 660 ignition. Check this out! I thought running that much advance would make your engine grenade.

rhino cdi timing.jpg

[edfmaniac]

Just pulled my plug after a long full throttle run and looking at the ceramic element, you can hardly tell it's been run. I think I may be a touch lean so I'm going from a 130 main jet on the primary carb to a 135 and using the drill bit that came with my carb kit to ever so slightly enlarge the jet on the diaphragm side. We'll see if that helps the ignition problems.

A local mechanic gave me some great ideas when I stopped by to show him my overall progress. He recommended relocation of the license plate to the oil tank along with a smaller light and integrated secondary oil tank mount, completely getting rid of anything hanging off of the tail. And instead of refurbishing my radiator to a naked aluminum, he brought up the idea of using motocross style split radiators. I like the idea because not only will it allow more air over the motor, but you can drastically change the way the bike looks by rotating them on different axes during mock up.

[edfmaniac]

Hmmm. I couldn't tell any difference after doing the jet work, even after dropping the main jet on the diaphragm side again and drilling it out to 1.95mm from 1.75mm.

[edfmaniac]

I think I'm getting closer to finding the high rpm stumble. The main jet on the left side carb is now drilled out to 1.55mm with a 1.95 on the right side carb and she's holding together through 8000. Another five or 10 thousandths on each side and we should be golden. First trip to the dyno is on Sat.

[edfmaniac]

Dyno showed an engine that was very rich up until 7000, then the mixture goes completely lean. It sounds a lot like the petcock issue except that I've fixed all of that stuff and the mixture goes lean too quick to be emptying the bowl. It's got to be jets and that means I have to go BIG!!! I'm already at 155 and 195.

Max HP reading was 50. Not bad for an engine that's spitting and sputtering at that output level. I expect to hit 55 once I get the jetting figured out, maybe even 60 if I decide to go with the Mikunis.

[samandkimberly]

You might want to look at the float needle jets as a point of obstruction. Considering that many (all?) Skorpions came with those vacuum fuel pumps its possible that the float needles are smaller than they should be for a gravity feed system. Of course, I'm assuming you're not running a fuel pump.

Also, are you sure you're getting solid spark right through where its falling on its face? Bad spark can cause all sorts of mixture readings. If its the ignitech I'd just raise the cutout up to 10K or something while you're dyno testing.

[edfmaniac]

I've checked the flow on the float valve by removing the bowl and watching it operate while hooked up to the tank. I think it's safe to say that's not where my problem is.

Now I'm getting adventurous trying to find the problem. First, I drilled a hole inside the bowl where the bottom meets the side and just over the channel that feeds the CV carb. I figured having the hole that low, instead of the one half way up the side of the bowl, would help the fuel flow. It did! The stumbling at high RPM is much less pronounced and actually goes away once I get above 8500. Since that improved the performance, the second thing I'm doing is to add another line coming out of the bowl and into the opposite side of the CV jet chamber. Fuel can't be a problem after this unless there is some weird, never to be found, freak issue.

That fresh set of Mikuni's is looking mighty good except they will also need to be jetted unless the distributors in Europe really have a good grasp on what to install for any given set of high performance components.

[edfmaniac]

Well......after virtually guaranteeing that fuel flow restriction wasn't an issue, and still not getting the engine to clear up completely on the high end, I decided to go back to the 135, 165 jetting that I ran before the rebuild and the engine came to life. Went down to 155 on the CV side and it got even better. Almost there!

Don't know what to think about the dyno mixture results though. Is it possible that losing fire due to crazy rich conditions gives a false lean reading?

[pod35]

I would like to ask; how did you decide on the oil level in the new tank - is it based on the volume in the tank or the height compared to the motor? I know that the level is important and do check it but I don't understand why it is so critical. I have a cunning plan for a new oil tank but want to understand the factors first.

[edfmaniac]

I'm no expert but I don't think oil level in the tank is that critical unless you are racing or driving at sustained high rpms. As long as there is enough oil in the system to keep the tank from going dry, your engine is safe. The more oil you have in the system however, the fewer times the entire volume gets cycled through the engine and the longer it will last. More volume will also allow more time for the air mixed in with the oil to separate before getting pumped back into the engine. As for my tank, I just mounted it and followed the normal oil change procedure except my tank needs the entire three quarts to start indicating on the dip stick.

[Wallace]

Keeping the oil at consistent temperature is more important than quantity but a quantity will hep control temperature!

[edfmaniac]

Just got back from the dyno and the bike is as close to dialed as it's going to get with the stock carbs. I'm generating about 56hp now. With the battle of opinions going on between Mustang dynos and Dynojet dynos, I really don't know what to compare my new numbers with. Before the rebuild, I was putting out just under 40hp on a Mustang dyno and the operator told me to add around 14% if I wanted to translate that into Dynojet hp. Now I'm using a Dynojet facility and am hitting 56. Worst case scenario, I've gained 10hp. That'll work! I should have no problem knocking on 60's door with the addition of some flat slide carbs.

[Srinath]

Wheels are certainly on my list. I'll probably end up with some GS500 wheels unless I go nuts and spring for some Marchesini's.

I own several GS500's and I can assure you ... the rear wheel of a GS is garbage. 3.5" and not any lighter than the 4.5 on the skorp.
Use Katana 4.5 wheels out of a post 97 kat. Its 3 spokes, straight spoke, not swept like the GS. They are cheaper than most anything else in the category.

Like this one -
http://www.ebay.com/itm/98-Suzuki-Katan ... 36&vxp=mtr

Cool.
Srinath.

[edfmaniac]

Thanks. Really hoping to treat myself to some Marchesini's for the KTM690 when I'm ready for the paint and powder coat. They are expensive but I want them unless some nice super moto spokes seem to find their way on the bike first and I'm happy with them.