The Hodaka Club Forum

what did you say the compression is? 60 will not run a Hodaka.

Hey Kevin, here's the timing procedure below under "Timing the Hodaka".

Max

PS--on the compression test, spray some WD-40 in the cylinder and kick it over several times with the throttle wide open and see what the best numbers are.

What Max said. One kick isn't enough, and throttle must be open. Kick vigorously until the number stops rising. It could take five or six but you will see what we mean.

I don't use Wd40 but do sometimes use motor oil. But only if I think the rings are not good. Anyway, oil is optional, multiple kicks is not optional.

OKay..Got it..set the timing at the top and they seem to open the most at the second mark to the left of the top...I set them at .014 in
there. I will kick it wide open throttle until it stabilizes and report back..Much thanks to all, for helping a newb out.. oh yeah tried starting fluid spray
into the carb and then kcked it several times...no joy.

If it won't start on gas it won't start on ether. There is something going on here, even if it is just grossly flooded. Your description of the timing sounds right and .014 is close enough to run.

By the way, when doing your compression test, empty the carb first and turn off the gas. No need to draw more fuel in when not needed. And when all else fails, start with a fresh plug, a dry carb bowl, and try push starting without turning on the gas. Assuming it isnt flooded it should not start but if it sputters or runs even briefly it was flooded.

Two items worthy of consideration.

1. A good double check on your timing is to simply watch the points as you rotate the flywheel in standard direction of rotation (operating the kick start will show you which direction that is). The points should just start to open as the line on the flywheel aligns with the first case mark it comes to. This visual check will confirm that your timing is close enough to at least run.

2. It is possible to install the floats upside down in some Mikuni carbs. If that has happened, the floats/float valve system will shut off the fuel flow wayeeeee before there is enough fuel in the carb float bowl for running. So check for that.

Ed

Ok quick update... Checked the spark..its good with plug outside the motor. compression is just under 90 after it stopped going up.
I put fresh gas in and checke the carb one more time..float needle seems to be working fine(goes in and out as the float moves).
petcock is good with good flow..still not starting ..about to throw in the towel..

Um, 90psi doesn't get it either. Something is amiss. You should be in excess of 130psi to run , even a little weakly. Also, though the needle moves, be sure the floats are not upside down... As Ed said.
Bob

I checked the old piston. It has 20 stamped Torwards the back on the top of the piston. I installed a stock piston. Is this .20 over? Should I go ahead and replace? The new stock piston has a 7.5 stamped.

You cannot put a stock piston in a bored cylinder and make it run. I would never spray starting fluid into the engine. When fitting a piston to the cylinder there are tolerances that must be met. Look in the manual or ask at a machine shop. -------Clarence

got it ...thnx

scarman, if the 20 is cut into the piston material it is indeed a .020 over (2nd oversize). I think the 7.5 on std. sized pistons is inked on and had to do with matching cylinders at the factory as there are small variations in the bore of new cylinders.

It appears the problem has been found.

It seems pretty sure that you have installed a "standard" size ("stock?") piston (nominal 56mm diameter) in a cylinder which was previously bored to " .020" over-size" (nominal 56.5mm diameter). That extra half a millimeter equals an extra .020" in bore diameter. Your posts don't mention having the cylinder re-bored . . . but I'm afraid we all sort of assumed that you had it bored and the bore job was done to provide proper clearance to the new piston. It now seems pretty certain we should not have made that assumption.

Your compression is wayeeeee low - as compared to what would be expected with a properly fitted piston and bore job . . . and a new set of rings with properly adjusted ring end gaps.

There are several Hodaka service providers listed on this web-site who can examine your cylinder and do a proper bore job and fit up to the proper size piston. I would urge you to contact one of them.
Ed

Let's verify some things.

Question, when you installed the new piston, did you measure the skirt clearance between piston and bore with a feeler gauge prior to final installation, and if so, what was the measured clearance?

When you installed the new ring/rings did you measure the ring end gap for each ring, with a feeler gauge, prior to installation, and if so what was the measured gap?

When you installed the new piston and rings, did you have the cylinder bored, or in the alternative did you deglaze the bore by honing?

Not trying to grill you on process, just establish factual benchmarks so we can proceed without further assumptions. If this is your first effort at a top end overhaul, it is going to be a learning curve thing. Everyone has been there too, so not to worry. Without a technical shop manual, top end overhauls can be challenging.

And I agree that if 90psi is all that can be generated, it won't work. I suppose it could run but you won't like it. I had a machinist years ago (1980) that thought he knew more about two stroke engines than I did so he disregarded my instructions to set up piston clearance of 0.003" and set it at 0.008". Two more thousandths and it would have been ten over, or first overbore. It ran and still did when I took it apart last year, but it always made low compression and rattled constantly. Could have shot the guy because the iron sleeve and new piston were the last Webco parts I could find. I plan to have it rejuvenated with nickel silicon carbide so maybe it will still live. Point is that if you did put a stock bore piston into a 20 over bore, you could have piston skirt clearances around 0.020 a 0.024" instead of 0.003 -0.004". You can see how that might not work well.

Let us know what you did or what you find.

I made a rookie mistake and just cleaned the cylinder...assuming it was a standard bore. The ring gaps seemed okay and I never checked the previous
piston because it was so carboned out. So live and learn a painful expensive lesson...measuring the bore it is 56.37..the old piston was 56.22.
Should I go ahead and go with a .02 piston and rings ? Or should I just send it out .?

Oh Wow. No wonder you have low compression. How to proceed depends on your pocket book. If it had a 20 over in it and the bore is clean and still close to spec as 20 over, a new 20 over piston and ring would work, just clean the bore with 220 W/D or similar, and start over. But you still have to check the skirt clearance no matter what you install, and the rings almost always have to be hand gapped to come out right, no matter what brand they are.

I would start with the old piston. Take the top end apart and put the old piston in the bore and check the skirt clearance at the top, the middle, and the bottom. Use a feeler gauge set and find a clean but very slightly firm fitment between skirt and bore. Check it several times until you get the feel for it. You will learn the process, which you need to know anyway, and you will know for a fact just how worn your old piston is. This will give you a starting place for selecting a new piston. If the bore can not be matched to within around 0.003" to a new piston, start over. Find a shop that can bore it correctly to match the new piston of your choice.

Maybe someone else can use you slightly used piston for a project bike.

Okay I will do that..I have it apart now..So use a feeler gauge with th old piston in? Can you explain a quick walk thru on what I should be seeing for a ring gap when I get the rings on? Sorry for the basic questions but I want to make sure Im doing it right. This is my first build with a bike I dont know the history on. First vintage build..its alot of fun but I ve got alot to learn..Shorty thanx for your time...

After my rebuild, I fouled out 5 or 6 plugs before getting my jets and timing set correctly. Buy a wholse box of plugs at the parts store and continue to change them out until Jetting and timing are where they need to be. Then make sure you carry a spare plug and a plug wrench wherever you go riding! You never know when one will foul out just because! ; D Victor

Update to my problem...After some great instruction from AZ shorty..I reinstalled a .02 over piston with proper ring gap and piston skirt measurement.\
Ran into a problem with the shift mechanism not installed properly when I took the magneto cover off to set the points. Got that solved
finally with a couple of phone calls and she fires up and smells brand new..Thanx again guys for all the help from a newb ...

Check the plug wire. Sometimes they will fire if twisted in a way that connects the inner core way with the plug out and the internal wire will seperate when you twist the wire back to the plug when screwed in