Ace 100 B+ Jetting Question

[cineburger]

After many hours of searching I have yet to find a simple explanation (for the simpleminded like me!) as to Hodaka's original intent in packaging 90,95,100 jets with the Mikuni VM20 carb. When would one normally use a lean 90 jet? Sea level?? Death Valley Rides?? Is this simply an altitude thing or is some other factor at work here?? I am assuming all else is set properly to normal specs. My problem is: easy starting; great running (on flat well paved road) in gears 1,2,3 wound out to full throttle (48-50 mph); no further power in 4th gear (nor 5th) and slight fading in RPMs and speed; immediate power dropping back into 3rd gear. Fresh fuel, new points (properly set), condenser, running new B7s plug; good fuel flow out of clean tank; carb cleaned ultrasonically twice; floats set to spec; this bike an unmolested 1200 mile survivor I got with original tires (since changed) whose internals look very pristine....the plug color is light brown, but methinks not light/grey enough and hence still too rich but I was interested to know under what normal circumstances one would use the 90 jet. I live at sea level Maryland. Thanks in advance for any help. PS I have tried the upper 3 notches on the needle clip with very slight improvement in each move toward leanness but still not solving the fadeout in 4th gear.

[Bullfrog]

cineburger,

Some of your comments give me heart palpitations. I urge a bit of caution, but folks here are the right ones to help you.

First off, you haven't mentioned what main jet you ARE running. It would be good to know that.

2nd - Leaner main jets (smaller numbers) are used to adjust for lower density air such as a) higher altitudes, b) hotter temperatures and/or c) higher humidity (more water in the air reduces the amount of oxygen available to the engine).

3rd - Light brown or tan is a GOOD color to see on your plug. Light gray is a warning signal . . . not a desireable target.

NOTE: Proper jetting has little to do with which gear you are in. The important question is: How does the engine run at a given throttle setting? Such as 1/4 throttle or 1/2, 3/4 or wide open throttle.

We can be more helpful if you tell us what main jet you have and describe what happens on a level road when you hold wide open throttle and run up to the top end of the third gear and then shift to fourth. What does the engine sound like as the revs start climbing in fourth? Please describe sounds and "feelings" (more than just "fade out" please).
Ed

[cineburger]

Bullfrog--thanks for the response; 1)I am running the 95 main jet; all others are also "stock/normal/original;" 3) my brown is sorta medium brown/tan not as light as the light tan (slightly grayish) that I see in many online pics of proper coloration of plugs; on a level road the engine winds out crisply through the whole throttle range in 1,2,3 gears to approx 48-50 mph; upon shifting to 4th gear there is maintenance of speed but no further acceleration immediately and a slight bogging tone and gradual speed decline as there is no apparent torque in this gear; it feels like it is trying to pull but has no strength; as soon as the speed falls off and it is clear that 4th gear cannot maintain existing speed, a downshift back into 3rd and acceleration and torque are back to "normal" with strong pull and clean running through the throttle range back up to 48-50mph; hope this clarifies

[cineburger]

PS--I am located in the Chesapeake Bay area--a high humidity area--which I understand may require a leaner setting; forgot to mention that....

[Al Harpster]

Won't pull in 4th or 5 the says lack of horsepower.

My experience with my B+, stock, says your jetting's in the ballpark. A 95 or 100 jet should be okay, needle position is fine tuning. Set both to the book...that's good for starts.

I think I'd start looking elsewhere. Won't pull 4th is pretty darn bad.

Cost some time & money, but compression test, crankcase pressure test, re-re check point gap, recheck for spark arrester blockage, air filter recheck.

Compression better be over 100 psi, pressure test better hold 6 psi for at least a couple minutes. I've found setting points to be a royal pain. That's ignition timing.

Blocked exhaust port or exhaust, crappy air filter makes for can't breathe.

Hope that helps.

[Joe Ormonde]

The one thing to check is IF your Bike has the Factory Spark Plug Cap. It screws into the Plastic Body , is Aluminum and are TROUBLE! You need to cut back the coil wire so that when you screw it back in it will pierce into a fresh spot. I have cut my coil wire back so many times that I FINALY Soldered a Brass Terminal to it with a rubber boot. What happens is that under load the Factory Cap just can`t provide the Spark Energy Needed . On the Hodaka Point type Magneto, the higher you rev the engine, the more it puts out. Since 1972, I have found that Factory Cap to be the cause of my Hodaka IMPOSSIBLE to tune 7 in 10 times! Joe Ormonde.

[cineburger]

Thanks Joe...my spark plug cap looks to be factory (compared to the ones pictured in all the manuals/parts books); next chance I get I'll give it a good going over and report back; thanks so much for the tip! this is the kind of experienced insider Hodaka info that only comes from a club forum like this and its very much appreciated by novices like me. Muchos gracias amigos....david

[Bullfrog]

48 to 50 mph in third gear? What is the tooth count on your sprockets?
Ed

[matt glascock]

You beat me to the punch, Captain. My Ace 100 will get to just over 50 at WOT in tall gear with my 190# rider and gear on the job. This sounds like speedway gearing with a non-pumped motor hitting the wall.

[cineburger]

Thanks Al--Compression=150 tested and retested; points and condenser replaced and settings spot on; exhaust system like new--cleaned inside and out; air filter very stock-checked about 6 times; have not done the leak-down test; that's next after I go thru the test rides with the other jets...
A bit more clarification--sorry for my inability to describe the sounds properly--the revs don't "start climbing" in 4th gear; upon shifting into 4th (and throttling down for the shift) the revs seem to try to increase but do not; the tone is slightly lower; there is no missing or sputtering or hesitation, everything seems to be firing properly, just no power to continue the acceleration; a more experienced ear than mine might have a different view of what seems to me to be normal 2 stroke acceleration in the first 3 gears and normal sounds accompanying that range on running....

[cineburger]

The rear sprocket is the 36 tooth version. Counted em...

[Bullfrog]

OK. That description of the situation and sounds provides another hint that your final drive gearing is probably set up for about 85-90 mph top speed . . . and a stock Ace 100 simply can not "pull" that sort of gearing. Waiting to hear the tooth count on your sprockets.
Ed

[Joe Ormonde]

Sounds like Gearing to me too. Still, go into the Library in the HPI Website and read everything. I never read these things back in the day and sure wish I had. Hodaka Service Bulletin 14 shows the cap and the problems related to it. If my posting this helps just 1 person find their Tuning problem, GREAT! Joe Ormonde.

[matt glascock]

Captain, according to the expanded Official Ace workshop manual (including MX), the compression range published is 80 - 150 PSI. My toaster tank Super Rat, which has been ported for reed induction by Hodaka Dave and is guaranteed to possess a face-melting power band - (ya gotta ride it sometime!) runs 158# compression. I run 94 octane pure gasoline at 32:1 with Yamalube R. I assume the compression range cited in the Workshop manual is presented so that the upper number (150 PSI) would be more appropriate for the Rat racing motor. Cineburger's ride is running 150 PSI which suggests a race-prepped motor (for reference, my Ace 100 runs 125 PSI). Now, two questions: 1) Is 150# compression high for a "stock" 100B? and 2) Could this be a pumped-up motor set-up for speed work as the gearing suggests? It would be cool if the top-end out-crapping problem is crappy 87 octane gasohol. Cineburger, in precise detail, what fuel/mix are you running?

[cineburger]

To all above--many thanks again for the education and the discussion; to my uneducated eye and experience the bike is "stock" on the outside; the rear sprocket is 36T; no larger sprocket came with the bike; I'd be happy to post a pic of the sprocket if this helps in the diagnosis; I'm using fresh 93 octane fuel (does have ethanol up to 10%); I just changed to 50:1 mix in a fresh batch from the previous 32:1 mix; I'm using Castrol Edge 10x30 full synthetic oil in the mix; 50-1 vs 32-1 did not seem to change the symptoms--maybe ever so slightly a faster run; and to reiterate--after about 5 kicks my compression tester reads 150 every time....still gotta count teeth on the drive sprocket later today sorry for the delay....

[cineburger]

Countershaft sprocket is stock 15tooth

[Al Harpster]

I ran my B+ on city sreets with a 30 tooth rear sprocket for years.

13 or 14 front I believe.

If you're geared way too high but have full horsepower you might expect to hit, say, 45 in third.

Just how fast can you get this thing to go?

Yes, 150 PSI sounds a bit high. I'd run it. You know you're not low compression. So that's out.

If your jetting's was way off you'd be running lean with a white plug or running rich & four cycling like crazy.

The stock VM20 carb with stock jetting should be fine for a starting place.

Those plug caps with the pointey threaded aluminum contact are suspect. Check it or replace it. Throw in another plug too if you like to cover all bases.

I weigh about 170. When my B+ was stock & good condition I could get 50 out of it. Maybe more, depended on red lights. It was no rocket as stock, but okay. Might have done 60 down a modest hill if I was foolish enough to try.

[taber hodaka]

I am going to say 150 compression is not hi.--------------- Clarence

[matt glascock]

Clarence, how do you account for the seemingly superwide range of within-spec compression (80 - 150 PSI)?

[cineburger]

Seems like my 4th gear fadeout problem's solution is leaning toward changing the gearing although I haven't addressed the spark plug cap issue yet (mine seems stock according to pics I have for comparison, but there seems to be no way to unscrew the cap from the wire to separate them as they appear to be sealed together at manufacture); but here's an additional question: according to my books Hodaka offered a number of different sprockets I guess for different rider weights and applications; I'm on the smaller end of the scale at 155 lbs so why would a 15T/36T "road" sprocket set be so deficient as to not pull 4th gear?? Is this designed for 115 pounders?? This is the stock setup Hodaka offered--what am I missing?? I know there are some possibilities like a PO changed the internal gearing in the tranny or there is some other internal problem gripping the gears inside with no noise to indicate it but these are pretty remote and unlikely....there must be many Ace 100 B+ bikes out there with stock 15t/36t gearing that can run all 5 speeds with modest torque in the top 2 gears...again thanks to all who are trying to help me here; despite the persistence required I am enjoying the process.

[matt glascock]

If you are running a 50:1 mix, you are running a richer mix (as in there is more fuel in a 50:1 mix compared to a 32:1 mix) which is more fuel than what would have been appropriate with the stock jetting so consider a few short jetting runs with progressively leaner main jets - but don't push it, go step by step. Do recall the fact that these bikes were initially designed to run on regular leaded gasoline at a 20:1 mix. 50:1 is a considerably (fuel) richer mix. Incidentally, the consensus here is that the best gasoline to run through these bikes contains absolutely NO alcohol for a variety of important reasons.

[taber hodaka]

Matt as the book states normal 150 to 80 .' . 150 is normal. I for myself would state normal as 150 to 110. To me 80 pounds of compression is about to the non running state. My Super rat manual lists compression by kickstart at 85 psi after 2 hours of running. Me from the old world a richer mix was more oil not less so a 50:1 mix is leaner. The bikes were not designed for to run on 20:1 we were using car oil some early bikes used 16:1. Junk oil then outboard did not compared to what we use today. Time for someone with more whiskers ??-----------Clarence

[matt glascock]

Thank you Clarence. It seemed to me 80# compression was almost too low to keep the ball rolling. I recall 16:1 was for break-in (500 miles) then 20:1. We always ran 16:1 but that was for race tuned motors that we flogged mercilessly. My version of "richness" deals with the concentration of gasoline in the vapor that gets squished into the combustion chamber with the oil just going along for the ride for its lubrication properties.

[Al Harpster]

The stock B+ plug cap's attachment is visible inside the cap with plug removed. A straight blade type screwdriver can unscrew it.

You may have some other cap.

How fast can you get this bike to go?

Re. Your question " could somebody have changed transmission gears?"

Yes, but

1- unlikely

2- the Racing Gear set for this thing is a closer ratio. This closer ratio set would not cause your complaint. I have one in mine. I like it very much. But it's not the fix YOU are looking for.

Again, how fast can you get this thing to go on flat pavement?

You should be able to run in all 5 gears and 50 should be obtainable no questions asked.

If you can't get to 50 no matter how slow the acceleration is you are low on horsepower.

Sprockets won't help horsepower, but can change acceleration rate.

My experience street riding a stock B+ says you are sprocketed okay for street riding on flat to moderate terrain.

[Bullfrog]

One item Al H. forgot . . . and so did I (till now) . . .

There are factors which "eat" horsepower - dry chains, bad bearings (anywhere in the drive chain from main bearings to wheel bearings), tire rubbing on chain guard, dragging brakes.

Short story - when I got back into riding Hodies after a 25+ year "vacation" from ALL THINGS MOTORCYCLE, I assembled a trail/race bike. When it was all done and I was rolling it to the back yard for photos . . . I noticed I had to "lean into it" just to push it. After I eliminated the tire rub on the chain guard and re-adjusted the brakes - it rolled almost as easily as my pedal power bike.

So, on level pavement - can you grab the handle bars with ONE hand in the center of the cross brace and push the bike with true ease?

Ed