Timing oh hs40 with solid state ignition

ELT

Active Member
#1
I have a freshly rebuilt hs40 with a solid state ignition. It starts easy and runs good but it doesn't accelerate as well as my hs40 engines that have points and I have timed right at .035. It seems like the solid state ignition timing is a little late. How do I go about advancing the timing a little bit with the solid state ignition.
 

delray

Well-Known Member
#2
from what little timing I have down with points to solid state. the points setup factory spec's run's about 15 degrees and the solid state runs about 20 degrees. if get into the Tecumseh motorsports coil that will put you about 30 degrees.
do you have this on the same bike? if not the weight,gearing...etc.. can play a big roll too.
 

ELT

Active Member
#3
from what little timing I have down with points to solid state. the points setup factory spec's run's about 15 degrees and the solid state runs about 20 degrees. if get into the Tecumseh motorsports coil that will put you about 30 degrees.
do you have this on the same bike? if not the weight,gearing...etc.. can play a big roll too.
The bike's are both 10" wheel rupps. A 70 enduro and a 71 hustler. The secondary spring is in the tightest setting. The 70 spanks the 71 out of the hole.
 

delray

Well-Known Member
#4
if I am correct the solid state engine might also have smaller valves. just depends on the year...etc. and if so the bowl opening/seat area will be smaller too. it doesn't take much to effect a engines performance over another one. just a bad responsive carb can kill it all.
 

cfh

Well-Known Member
#5
What i've noticed on the small valve HS50 are on the cams. On the exhaust lobe, they have a built in compression release. Engine runs great at low and even mid RPM. but at full throttle it's lethargic at best. I just modify the cam lobe and that problem is fixed, engine comes alive. This is mostly HSSK50 engines i've noticed this.
 
#6
What i've noticed on the small valve HS50 are on the cams. On the exhaust lobe, they have a built in compression release. Engine runs great at low and even mid RPM. but at full throttle it's lethargic at best. I just modify the cam lobe and that problem is fixed, engine comes alive. This is mostly HSSK50 engines i've noticed this.
Thanks for this ^^^ this confirms a feeling I have had for a while. I have a small valve Hs50 that runs like a top but kinda falls off. Pulls good down low and mid range though.
I was going to put valve springs in it but now I am rethinking this.
 

cfh

Well-Known Member
#7
You can test for it. With the head off, on compression the exhaust valve will 'rock'. that's the relief. It's really easy to remove. But you have to take the cam out to do that. Also you can use a compression tool to check. Without relief you should be 90 to 120 on the compression measure. With the relief it's only 60 ! Also you can feel it when you pull the starter cord. The ones with the relief feel different, softer.
 

ELT

Active Member
#8
if I am correct the solid state engine might also have smaller valves. just depends on the year...etc. and if so the bowl opening/seat area will be smaller too. it doesn't take much to effect a engines performance over another one. just a bad responsive carb can kill it all.
You might have put your finger on something. The carburetor I used on this engine was the one in the parts pile with the correct choke lever on it. It runs fine but it might have came off a smaller engine. I put another carburetor on it that I know was on a hs40. I'll see how it runs in the morning.
 

old shed finds

Well-Known Member
#11
I have done the same thing.... It was carb issue. ... Small ventury in my carb not near enough flow to bring my engine alive. ... Too small of carb ran my engine lean and hot...... Caution...
 
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