3xv: Project Phoenix

[Steveog]

Mostly good on test start. (No air boxes for test) It started fourth kick with the Zeel in place. Got the same overflow leakage from RH carb as I did right after rebuild. Wouldn't settle to an idle. Responded to throttle, but wanted to run at 7K. I shut it off after about 30 seconds. Switched back to -00 ECU. Same thing, just not as intense as with the Zeel. HA.

Yes, the TPS was shut-off. Didn't keep the -00 box hooked up long enough to notice anything except high rpm start-up.

Its got to be the carbs. Fuel overflow and screaming start-up are symptoms with which I'm familiar.

I had the bike disassembled down to the cases and the running chassis. No, I did not clean the carbs thoroughly before reassembly. I did replace the float needle valves though. Stock sizes.

I can't imagine the fixed air jets #20 in the VAJ blocks causing this kind of running.

Carbs were synced, cable pull seems on-target.

I'll start on the RH carb, Monday. Bet that will solve the problem. Then, get the idle and slow circuits tuned in...again.

Enjoy your weekend.   

[Martin77]

Is the r/h carb shutting off properly with the new cable fitting? idle settings should be pretty much the same as stock in my experience.

[Steveog]

Yes, Martin. Slides on both carbs fully open and fully close in sync with each other. I messed around with the adjusters on the RH carb when the bike was running at around 7K, I could only make to rev more.

With the TPS gone there is no idle adjustment screw. The RH slide was on the dead bottom of its adjustment. I didn't try the air screw.

I believe some crap got into the float needle seat or fuel passage when I had the carbs apart. That would explain the overflow. Why I have a high rpm start up is a bit of a mystery. Perhaps my throttle cable mod threw things out of whack. I'll know more when I dig in.

No leaks in the new cooling system.

Thanks for checking in on me.

Steve

I just realized that I may have been misleading. I did not tear the bike down to the cases. The cylinders were left in place.

[Steveog]

Note: My four year old grandson wanted to see the motorcycle(s). When we got to the shop, the RH carb was still leaking, despite the fact that I had turned the tap to "OFF". (I had a drain pan under the overflow tube.)

New mystery.

The LH carb was solid.

Steve

[ybk]

Junk can still get past the filters and affect the needle, otherwise float level (go to the minimum height, 15 or 16mm I think?)

[Martin77]

What fuel tap are you using, the standard Yamaha item?

[Steveog]

Karl - Yes. The float needle was the problem right after the initial rebuild. The float heights are good. I should have gone over the carbs when I had them off to refit the stock reeds. Lazy = Dumb.

Martin - I'm using an RGV tap. Guessing the dribble was coming from the fuel left in the lines and float bowl.

The over-rev on startup has got to be in my throttle cable. There's a weird little wheel inside the splitter that pulls the individual cables. I'm betting that's my problem area. Must fit a TZ dual cable system. The stock thing is making me nuts.

Thanks for your ideas and questions.

Enjoy your day, boys.

[James P]

Can you explain the 1 KT Formula 3 mod?

Basically, it involves changing the source of the atomiser air supply from 'external' to 'internal' (relative to the air box). The steps listed below may help you to visualise the modification:

1. Remove the brass plug from the atomiser air passage on the front of the bellmouth casting (easiest way is to remove the bellmouth casting from the carb body and punch out the plug from 'inside')
2. Block off the 'normal' atomiser air passage entry (the brass tube on the right-hand side of the bellmouth casting)
3. Replace the standard bleed-type atomiser with a primary-type atomiser (use Mikuni 159-series, which are available in a huge range of sizes)
4. Replace the standard needle with the Formula 3 kit needle (Mikuni 5EJ48), or use a needle of similar length, thickness and tapers (e.g. 5EJ11 etc.)

If you are using a non-3XV TM28SS carb (e.g. 1KT, 2YK, 2YY etc.), Step 1 will also involve punching out the main air jet which is pressed into the same passage. Note that 2XT carbs have brass plugs and main air jets which can be unscrewed (no need to punch out).

The modification means that the atomiser air supply will come from inside the air box instead of from outside. The advantages of the conversion are:

a) The complete elimination of all air jets
b) The use of atomisers which are available in a large range of sizes

Some people may want to argue that eliminating air jets is not an advantage, but I have found that this simplifies carb set-up considerably. Admittedly the 5EJ48 needle is not widely stocked, but it should still be available from Topham in Germany.

The 1KT Formula 3 kit manual explains how to do the carb conversion but if you have tinkered with these carbs before, Steps 1 to 4 above should be enough. I prefer to permanently block the normal 'external' atomiser air passage by removing the brass tube, drilling and tapping the passage and inserting a grub screw. However, securely crimping the rubber hose will have the same effect on a temporary basis.

If you need any more info, please ask!

Regards,
James

[Steveog]

Thanks, James. Well written instructions.

I'd like a second set of carbs for such a mod, but I'm definitely in a "simplify" mood these days.

Fighting through a lot of changes at once right now. May have more questions on this, later.

Really appreciate the time you're taken to explain this.

Steve

[Steveog]

Is the r/h carb shutting off properly with the new cable fitting? idle settings should be pretty much the same as stock in my experience.

Very close, Martin. The cause of the high revs on start up turned out to be the throttle junction box. My new adjuster for the RH carb was so far off that it jammed the wheel inside the junction, pulling the slide up. A bit of fiddling and the two cables lined up. One kick and a steady idle (tick-over) @ 1500 RPM. This was on the choke with what was left in the float bowls, so not real test, but I know I'm on the right track for a test ride tomorrow.

Karl. You were absolutely correct about a dirty carb. I cleaned the (RH) carb completely. Overflow, solved.

Many thanks, gents.

Steve

[Martin77]

Nice... I thought it was probably something like that.. always listen for the double 'clack' sound of the carb slide snapping shut when you release the twistgrip..

Is it soon time for some test riding?

[Steveog]

Yes, Martin. A test ride or two this afternoon. That throttle cable still concerns me. Because the adjusters on the RH carb were causing the over-rev, now that I've got the cable-pull balanced I can't really use them to adjust the idle.

Perhaps the air mixture screw can help me dial things in. I've also gone to 12.5 pilots.

I'll post the results. Probably no plug chops today. Just need to see how it runs and cools in general. The temps here today will be around 32C+. A good test for the new radiator.

Thanks, as always.

Steve

[Warwick]

Steve, if you are sticking with the 28mm carbs it might be worth taking a close look at the casting of the lower cyl carb body. You will see that it has the basic architecture to allow you to modify it to allow the fitment of the same kind of slide stop screw as the upper carb if you wanted to explore that option? Maybe even just look at using an upper cyl carb body for ease? Either way, I think it would be worth looking at replacing your home-brew cable with a twin pull throttle and separate cables as and when you can to make life as easy as possible?

What's the rationale for the 12.5 pilots? I'd have thought it wiser to run bigger than stock pilots if you can get away with it to give the motor a bit more lubrication on a closed throttle? 

[Martin77]

Would it be possible to fit a idle adjuster with one of these kits?

https://www.amazon.com/Motion-Pro-08-0045-Idle-Screw/dp/B000GTTFME

[Steveog]

Good news on the test ride, boys. Air temp 32C, humidity high. This is the kind of environment that would choke the original version.  Zeel ECU, Toomey Radiator and Scitsu temp gauge installed. Running the air boxes and filters. Started first kick, but would barely idle (1K). Loaded up a bit and felt rich (spongy) at lower rpms. There is no leakage or other obvious issues.

GOOD NEWS: Te bike absolutely, fucking rips from 7-11.5K and was still pulling hard. Front end got light in second gear. This thing never wheelies...until now. No I did not pull on the bars.

Warwick, I was planning on a dual pull throttle, but I got my DIY version to work for the short term. The reason I went to #12.5 was advice about going down on the pilot if the air screws were backed out further than 2.5 turns. I was there on both carbs. Yes, I remembered your advice about staying rich on the pilots, but you can see how the two pieces of tuning advice might have conflicted. I was originally going to run #20 pilots. Could it be that the poor low end response is that I'm too lean? That wouldn't seem to explain the bike loading up a bit and smoking more at low rpm, but I'm willing to listen.

Yes, I'm sticking with the 28's for now...finances. I wondered if an idle adjustment screw could be added to the threaded blank spot on the RH carb. Will give it a try.

Thanks for the link, Martin. Will get to that after Atlanta. I finally know what your cylinder/head tuning feel like. "They feel like Victory." I want to move on to the rear ride height, but feel one more day on the engine would be a good idea.

Now. I'm a bit confused about the throttle response from 2-7K. Its mushy, but clears up with vengeance. Warwick mentioned that might be the case running only the fixed VAJ air jet. I'm using the stock Zeel setting #1. I feel this is all about jetting. The rest of my current setting are posted.

I am very happy with what you guys and others have helped me build. Phoenix has risen, if a bit grumpy getting out of bed. Thank You.