Thanks. That's a ton of info. Having limited choices is a good and a bad thing. I have a Virgo 750 that I turned into a cafe racer. I put 2 mikuni vm34s on there. As we all know, the possibilities on mikuni round slide carbs are endless. It was so hard to dial them in. Too many choices and I jad to become sort of a round slide expert to get that bike fueled properly.

 

I got to open the bike up and let her breathe today. It runs smoothly all through the rev range. However, above 7100, she falls flat. I know that our bikes are tractors, but I'm trying to extend that power band further. I definitely think KLXSTER is right that it is under fueled with the DJ140 main. I'm gonna bump her up to a 146 as soon as my package gets here from jetsrus.com. I'll update when I get that installed. The bottom and mid are really strong. I was at 26mph in 6th gear and opened the throttle wide and she picked up quickly and took off. I also think that when my bike feels at its best, I am going to take it to a dyno for a run. Does anyone know what a base run costs these days?

 

You should only approach a dyno shop after "arming-up" with the knowledge that will allow you to tell them exactly what you want for your money.. There are many reasons for this.. If you don't "arm-up", expect to be disappointed, possibly fleeced, and/or presented unusable data..

For what you want, 50$ to 100$ is the range to expect.. When you get ready to do this, I can give you the information you'll need in order to start making the phone calls..

 

I'm going to hit my hundred mile break-in by tomorrow so I scheduled with a dyno for next Wednesday. What am I looking for in a run. My instincts tell me that a 4th gear run with a slower roll-on is the way to go so I can see the AFR across the entire range rather than a wide open run. I'll wait for guidance, though. I don't want to pay twice.


Also, on a different note, I need to quiet this thing down a little bit. Does anyone have any info on the quiet core tip for the powercore4? Does it mess with the airflow at all? Can I run my spark arrestor in it? Lastly, do they work? I'm not trying to make my bike super quiet. The 351 just tipped it into the obnoxious level any time I'm on the throttle.

 

I'll cut and paste previous "dyno advice" posts of mine as I can find time - But the only goal is to acquire the .DRF files, from each pull on your bike, onto your brand new, still in the package, thumbdrive. The DRF's are the raw data files. You can use DynoJets' freely downloaded WinPep 7 to view charts any which way you want from the DRF files. You can also email your DRF's for others to overlay onto their DRF's.. For instance, you could send them to me and I could instantly show your curves and my bikes' best curves on one chart for all to see..

If they won't do that or say they can't - move on.


Dyno shops usually follow a "business plan" when dealing with new customers, with the goal of making you a repeat customer.. When you approach them armed with knowledge and specific requests, you throw them off their game, so expect varied responses..

Please understand that we have a great need for accurate, trustworthy, dyno information on 351's. All current and all future members - probably the entire Forum - will want to view your dyno data, if it is usable..

 

Just before you have them load your bike onto a dyno:

Be sure rear tire air pressure is 30 PSI.

Oil the chain - it must be oiled well regardless of whether or not you have an o-ring chain. However, it must not be dripping of oil - you don't want it slinging oil all over the dyno.

Pull out any screen or obstruction in the slipon - if they are doing their job correctly, they will snake a copper tube AFR probe all the way up to near the exhaust port in the header..

Take a brand new USB Thumb drive, still in its' packaging, for them to open and load your data onto.

Notes:

You will be getting at least three "pulls" .. The operator should be putting your name on the data files and "session config" into the dyno - so all your data has your name on it.. The bike must be at operating temp - if they are doing their job correctly, they will be using a handheld infrared temp probe to "hand test" the cylinder temps. . 4th gear pulls are the norm. Once the operator thinks he has good pulls, he will quit - what happens next determines whether your money has been well spent or thrown away.. You now need to get the DRF data files on your thumb drive - NO CHARTS, NO PRINTOUTS, NOTHING ELSE.. Go home, install WinPEP 7, load up your DRF, set the parameters you want for viewing your curves, enjoy..

 

If, for whatever reason, you are not going to be getting your DRF's, Put TRQ, HP, and AFR on separate charts (3 charts),, Correction Factor must be SAE - "CF:SAE" on the chart. Smoothing value of 5.. All environmental conditions listed at bottom .

Among the "environmental conditions data" you will have the calculated correction number - this data provides validity to everything that happened to your bike while on the dyno, and credibility to the results..

 

Oh, BTW, I am old and crabby..

 

And you also provide the most comprehensive tuning information on this site.

 

Thanks..

From the link on your signature line - I sure hope I can ride like you do when I'm in my 70's..