I'm getting some break in miles on my B+ build and so far its running great. It will be another few weeks before the season really gets going and I'll plate and insure the bike then. For now I sneak it up and down my road a few miles at a time. Today brought that total to about 24. I've been wondering how hard to push the engine at this point? I've been holding it to 40mph indicated as a max speed, varying the rpm, lots of shifting, no lugging etc.
I purchased one of those small inductive tach's to try. This one is from Moose although there are others that are similar in our catalogs.
Today I made up a small plate and bolted it to a bar clamp bolt and also strapped one of my GPS on the handle bar.
I'm running stock 15/36 sprockets. At 40mph on the speedo my GPS is reading 65 kilometers per hour which doing the math is 40.3mph so the speedo is dead on at this speed. The tach is showing about 5000 rpm at 40mph.
Does this sound right? It seems legit as the tach shows idle at 900-1000rpm. (the tach has 3 settings and this one is the only one that provided a reasonable idle rpm.
Also: any advice as to how many miles before I can start pushing the rpm up? And what would you say is a safe cruise rpm once broken in?
Sounds OK. My Wbat 94 has an inop speedo and I added a Moose tach/hr meter and calc'd the speed:rpm from the ratios.
On my bike, the total gear ratio in 5th is given to be 10.45:1 (check yr specs).
37mph=5000rpm. 44=6000. 52=7000 and 59=8000. In 5th gear.
HP peaks at 7500 or 55 mph
Torque peaks at 5900 or just shy of 44 and probably is a "reasonable" cruising speed.
Thanks Bill, you encouraged me to do the math even though it makes my head hurt. Allowing for minor errors in radius and therefore circumference of the rear wheel/tire measurement --- Primary ratio 3.63:1 Final ratio 2.4:1 = overall ratio of 8.71:1 in 5th gear (which is 1:1)
Radius of 12.25" = Circumference of 76.93" Wheel revolutions per 1000 rpm = 114.81 (1000/overall ratio). Miles per 1000rpm per hour = 8.363 and therefore 5000rpm should be 41.8mph. So what I'm showing on my speedo, GPS and tach is pretty close and believable.
And the specs state that max torque is at 5500rpm which works out to 46mph or 74kph.
If the bike is happy to cruise at this speed with occasional spurts up to 50mph I'll be pleased.
And advice regarding the break in is still appreciated.
You have completed several "hot/cold" cycles (and several miles) . . . it is time to "wring it out" a bit on one or two more short rides. Bring the engine up to normal operating temperature, then do a couple of acceleration runs through 5th gear with all the gusto the machine can muster. Take it home and park it over night then do the same thing the next day. Then you are ready to go . . . break in complete.
My 2 cents,
Ed
Ken--
That sounds reasonable. Now we know for certain. My tach is mounted in the center of the Speedo, betw the Odo and the Trip odo. A temperature gauge goes over the steering stem where your tach is.
Ed--
My four-stroke break-in is to not run long periods at a constant speed and to vary the throttle and rpm frequently. And every now and then redline the engine. Been doing laps in the pasture and riding trails near home. I'll finish up with a couple of 10 and 20 mile roadtrips, which should finish off my 28:1 breakin premix, then I'll consider taking the oil to 32:1 (NOT 32 and 28 :1)
Last edited by Bill2001 on Mon Apr 10, 2017 5:34 pm, edited 1 time in total.
I don't think there is enough difference between 32:1 and 28:1 to make any difference. I would think if you wanted to run richer it would be during breakin. 28:1 is richer than 32:1 The biggest thing here is to not be running lean regardless of your mix ratio. -------------Clarence
Cool, thanks Ed. There were 5 heat cycles before I was able to put on any riding. (waiting for some snow to melt of our road)
Next time out I'll follow your procedure. I know everyone has their own thoughts on this but this is the first engine I've done of this small displacement and running this tight a piston clearance. I appreciate the experienced advice.
Primary gear ratio for the 100B or 92B+ listed in my information lists 2.82:1 . The 100B or 92B primary gear ratio is listed at 3.63:1 at least in my data. That is one of the changes in the B+. Ken how tight is your piston clearance ------------Clarence
The owners manual originally called for 500 miles break-in at 16:1 and 20:1 thereafter. This, of course, was predicated on using simple motor oil and not modern formula two stroke oils. But oil quality aside, there is a world of difference between half a dozen heat cool cycles and 500 miles. The short term heat cool cycle break-in regimen is targeted at racing equipment set up to different clearances, and intended to be used in an engine of a very finite service life. For a Wombat, the idea is to break it in so that you get a really long service life out of it, so that you don't have to rebuild it every season. I would continue to break the engine in over another several hundred miles gradually increasing speeds and loads. In other words just ride it like you have been, and stay off the interstate.
Also, break-in at 32:1 followed by normal use of 28:1 is backwards, as Clarence points out. Ratios are expressed in these terms: 28 parts gasoline to one part oil, etc. The higher the gasoline number compared to oil, the leaner the mixture. I would agree generally that there is not a lot of difference to be found between 28 and 32 to one, but would have no problems using the 28 ratio if it makes you more comfortable and the bike runs well. Vintage high performance two strokes running on modern synthetic or dino oil are often run at 20:1 or even 16:1, but that's for racing. I wouldn't go leaner than 32:1.
Oops... I did get those oil ratios ack-basswards. Although we tend to discuss ratios as ratios, I tend to think in terms of oz-oil/gal-gas, such as 4oz/gal or 4.5oz/gal. I'll go back and correct that.
"Temperature" refers to Exhaust Gas Temperature or EGT. I installed an EGT gauge to indirectly monitor mixture and piston temperature. Altogether too many reports of piston seizure!! I'll see what this shows.
Do a Search on "EGT" to find the thread on this. I think the title is "Cylinder Temperatures".
Seizures result from several things, not all of which are directly reflected by EGT. For example, so called cold seizures or four corner seizures don't occur due to high combustion temperatures, and are the sort of seizures more commonly found during break in than well after an engine is thoroughly run in. Unless you are logging data on a test bench, I am not certain what EGT would show you, and unless you also have a warning device or are looking at the read out 100% of the time, you probably won't see a significant rise in EGT in time to catch a seizure before it happens. Normally you only have a two or three second window of time to see, hear, or feel a pending seizure resulting from oil film failure. About the only thing I would expect an EGT to reflect in real time is detonation, and while detonation can result in seizure, seizure is more a by-product of piston failure from detonation. That is, detonation doesn't cause seizure per se, but melting the piston can.
Without reliable data, EGT's are just a factoid. For example, a turbo diesel's post-turbo EGT may normally be in the 750-950 degree range, which is a fairly broad range. But if the temperature spikes to 1,200 degrees, is that a sign of trouble? Not necessarily. Even temps as high as 1,400 might be acceptable briefly under the right operating conditions. Without more information regarding what the engine is doing at the same time temps are seen, the temps alone tell you little.
Same for a two stroke, but the temps would be particular to that breed and displacement of engine. That's why I suggested that an EGT might be very helpful on a test bench where operating conditions are concurrently recorded. Once EGT can be plotted against other parameters, EGT might then be used as an indicator or warning if it is repeatedly seen in combination with other data. Without others factors known, EGT alone isn't all that helpful.
Seizures are generally avoided by proper clearances, proper lubrication, proper fuel octane, ethanol avoidance, adequate jetting, and proper break-in regimen. Short of abuse, I don't believe I ever saw a factory two stroke seize under power. Almost always, it was after a rebuild.
A couple of commenters have talked about one pre-mix ratio being "lean" or "leaner" than another. I would caution against such "short hand" in comments. While 36:1 pre-mix is "leaner ON OIL" than 26:1 - it is "richer" on gasoline going through the main jet and thus is "richer" when thinking about jetting. So when using the terms "rich" and "lean", it is important to maintain close "contact" with exactly what is being described. Are we talking about oil? Or are we talking about the fuel/air mixture which the carburetor controls? Or are we leaving it to the reader to discern what we mean?
While I can't offer definitive data . . . I'm sticking with my recommendation for several heat cycles and inclusion of some high rpm "excursions" to complete the "break in". I have suspicions (but no proof) that the original factory recommendation of 500 miles "break in" was there for two basic reasons: 1) abundant caution and possibly, 2) miles at low loads to burnish transmission gears (also with abundant caution). Since most Hodies are well into the transmission burnishing by now, top end "break in" seems to be the primary concern (at least to me). I am not convinced that long term longevity (redundant?) is improved by an extended "gentle" operating period. My own satisfaction with longevity of top end reliability and wear seems to be related far, far more to regular air cleaner servicing than anything else.
Ed
Very good points, Jack. In my case, the supposedly fresh engine in my new bike wasn't, and I suspect that the piston was previously seriously seized. That piston was waiting to seize again. I've since redone the top end to my satisfaction and verified that the bottom end is not about to fail (plan split the cases during the horrid hot part of Summer).
The EGT may well be a Fools Errand, but I think that it will be useful to monitor, even indirectly, the mixture/top end temperature. The gauge has an adjustable setpoint where the display goes from Blue to Red and records the peak temp during that on-cycle. Of course I'll adjust and evaluate the mixture the usual ways Zand use the EGT as a known parameter. We'll see what we see.
I'm a gearhead and like gadgetry and like puttering. AFAIK, this has not been done on a street motorcycle, much less a Hodaka. EGTs are more in the realm of snowmobiles and ultralight aircraft.
I'll report back.
A few thoughts--- interesting discussion! I didn't mean to open a can of worms with my break in query but in retrospect I guess its a bit like asking what oil everyone likes.
Regarding seizures: we see several each winter on sleds. Most can be attributed to dirty carbs. Improper storage leads to plugged pilots and people not recognizing the tell tale signs when they start them up for the first ride. Too anxious to get out and go and soon enough the damage is done.
Although for something different I had an odd failure this past winter. PTO side melt down, appeared lean when disassembled but couldn't find anything in the fuel system as a cause. Machine is electronic fuel injected with an electronic oil pump as well. Via the laptop I'm able to run the oil pump without the engine running and confirm flow. Also able to pulse the fuel injectors. Turned out the PTO crank seal was gone. It had a small perfectly round hole in it...any guesses? Crank bearing failure that ejected a ball bearing through the seal. Ya, its the first time we've seen it too. And on a brand new 800cc machine with very low miles. Bearings made in China? No comment on that or the make of snowmobile but I thought some of you might find it interesting.
We never see outboard seizures, most often they just plain wear out. Too many hours. ATV's? Its usually dirt ingestion. Motorcycles? We are tuning fork and big "S" dealer so its pretty much oil and tire changes.
I asked Bill about the temp gauge because I remember reading Gordon Jennings on the subject who said that cylinder head temps were not worth monitoring. He said that by the time the cyl hd temp was too high the damage was done. He went on to talk about exhaust temps and the usefulness of watching them. And food for thought: that snowmobile I am talking about has a temp sensor in the exh header that feeds info to the ECU which in turn will actually shut off the spark if the temp gets too high. It also records how many times the unit has experienced an "Overheat Shutdown" and we can read this with the laptop. As well as a total RPM history and TPS history. (Obviously it isn't a foolproof system)
Different times in the business from when Hodakas were new.
You are right that mostly, EGTs are found on sno-mos and things like ultra light engines, but what those two toys have in common is fairly constant rpm in use. Aircraft particularly don't change rpm often, and snow machines have constantly variable drives that keep engine rpm relatively constant within a narrow range, allowing the belt drive pulleys and load dictate speed over the ground. Having a pilots license and a Polaris, I am familiar with the operation of each example. When EGT rises but engine load remains constant, you may have a problem, hence their use.
In contrast, the rpm of a direct drive device like a motorcycle is usually all over the map unless trying for a beer run time record. Not saying it is a fools errand. Information has value no matter how derived. Go ahead and use it, and let folks know if useful info comes of the application.
Question for Capt. Ed--given your abbreviated break-in period I was wondering when one should get off the 16:1 oil mix ratio and move up to 20:1 or beyond??
Finish the 5 or 6 complete heat cycles - which include some "wring outs" to full RPM - then make the switch to your chosen "standard" pre- mix ratio. If you filled the tank with 16:1, run it all before making the change. My 2 cents.
Crank bearing failure that ejected a ball bearing through the seal. Ya, its the first time we've seen it too. And on a brand new 800cc machine with very low miles. Bearings made in China? No comment on that or the make of snowmobile but I thought some of you might find it interesting.