Engine Mechanical TopicsDiscussion for motor builds, cams, head work, stripped bolts and other engine related issues. The good and the bad. If it goes round and around or up and down, post it here.
Here's the dyno graph. I honestly think the jetting may be a little rich also. I'm currently getting 34mpg trying to ride as easy as possible with this new motor build, enjoying twisting the throttle at times though...
Posting this on my cell phone so hope the photo works out ok. Run labeled "002" was setup with a 220 main jet. Then we tried increasing the fuel and went to the 235 main. 50 idle jet both runs. For such a huge increase in jet size hp and torque hardly moved. I'm thinking about going a little leaner and possibly going less aggressive on the DTT to avoid ping.
Actually, the graph is showing lean AFR 14+ all the way across; the AFR line should be floating around between 13 and 14 at WOT. I would check the diaphragm for any tears or leaks, look like air is getting in. The fact that the AFR line didn't change from the 220 to the 235 is telling us that jet size has little effect on the AFR; something else is interfering it would appear. How does the bike start and idle? partial throttle response good? what do the plugs look like? are you sure the slide is coming all the way up at WOT? are you running all OEM parts in the CV carb? CV40 or 44?
For reference, I have attached a dyno sheet from a 95" with 37 cams and Mik 42 carb; not a CV but the graph would look the same with a CV properly jetted. Check out the AFR.
The DTT is currently set at 2/2
As far as an air leak of some kind, when I had the carb off doing the jetting I inspected the diaphragm. It looked good, no tears. Blowing into the slot in the throat of the carb causes the slide to rise. Plugs look OK in my opinion. They only have about 500 miles on them so they don't really have a good burn yet. If you think it would help, I can post a photo of the plugs. Bike starts and idles very well. Imo mid range throttle response is good too. Stock CV carb with stock internals.
Very infrequently the engine will puff thru the carb while accelerating. Idk if that may be a tuning issue or that it's just 35 degrees here in the morning during my commute. Also of course changed intake seals and intake flanges with these new heads
Last edited by SafetyFifth; 02-06-2017 at 11:03 AM.
I know how the CV works; question was are you sure that the slide is all the way up at WOT?
Maybe I am missing something but something isn't right. AFR showing lean with a 235 main and no real change when main goes from 220 to 235?? I run an all bore 107 with a CV44, 48 pilot and 215 main (124TQ/110HP) I know, not apples to apples but at WOT both motors are on the main. AFR sitting about 13.6 all the way across at WOT. Mine will puff through the carb, sort of a burp, every now and then but at cruise; I still haven't figured that out. Needle maybe but it doesn't happen enough to bother me. 38mpg and I don't baby it ever.
If the diaphragm has no tears and the slide rises with air blown in the slide port. What could cause the slide not to rise all the way up at WOT? Short of me paying for another hour of dyno time and having the air cleaner off or revving the bike to WOT at idle idk how else I could check. Next time I ride the bike I'll look into a possible intake seal leak. I'd think I'd be having other issues if those intake seals were leaking though. But it's worth crossing off the list of possible issues
Last edited by SafetyFifth; 02-06-2017 at 12:18 PM.
If the diaphragm has no tears and the slide rises with air blown in the slide port. What could cause the slide not to rise all the way up at WOT? Short of me paying for another hour of dyno time and having the air cleaner off or revving the bike to WOT at idle idk how else I could check
I don't know, vacuum leak somewhere could do it; probably not an issue. I would be more concerned about the jetting anomaly.
The last time I tuned my 107" motor, I kept going up on the main with similar results. I checked the diaphragm and there were no holes or tears in the diaphragm but there were some tears at the edge which I thought would seal when the cap was tightened but the problem persisted until I replaced the diaphragm. I had some pictures but can't find them. Check that diaphragm closely; a pinhole or a poor seal at the cap could cause the problem.
Thanks for the info man. Going to look into the possible issues with the diaphragm and intake seals Wednesday when I ride the bike next. I'll post back with what I find
Thanks for all the replies guys. Let me address a few things that jumped out after reading all your inputs.
The cylinders and heads are extremely low mile takeoffs. They might have 30 miles on them. Buddy of mine bought a new bike and had the dealer do a motor build before he took delivery. With that being said, Im not hip on boring these cylinders or doing any kind of headwork. Mainly cause these parts are practically brand new.
As far as why I dislike adjustable pushrods, the setup is a pain (IMO) and also dont want to have to deal with locknuts getting loose over time. Just think solids are stronger and less of a potential headache.
Also should point out the bike is carbureted and has the stock ignition module. I absolutely will be having the bike dyno tuned after I do the break in.
Looking into different cam options, so far the andrews tw48 looks like a solid choice. 8.94 corrected compression with 184.4 cold crank compression. Can you guys recommend anything different. Looking for midrange power, ideally turning on at 2k or so and building on up to 5kish. Also a cam that can take advantage of this better flowing 06 head
Does aftermarket offer "perfect fit" pushrods? Or if I go with anything besides a bolt in cam am I stuck running adjustables?
Thank you!!!
I have a 2010 dyna built with a stock 96ci cyl and heads. Andrews 48H SC heavy breather, V&H bigshots and a good dyno tune on my SERT. I have a very strong midrange and lots of power. 85hp and 102ft on the rear wheeln
do you have your throttle cables adjusted correctly so that the throttle is 100% open, hitting the stop when you twist the grip all the way? how are the afr samples being taken, like previously said, the line on the graph is lean. need to verify accurate afr data, could be a wonky sensor in the afr box, or could be an air leak in the intake system,OR since you dont show a graph with afr from both cylinders, one might be running richer or leaner than the other, which in istself is another story,,,,,try to get some more data.
m
ps, i would have recommended the 37's for you too!!!
02-06-2017, 07:42 AM
