igitions for Hi performance?

F

Flyman

Member
Hey I,m a new guy to these little bike engines.But have built
many a racing kart engine.I ordered a cheap bike kit & it
will be here Tues.

My question to you motor heads, Does a guy really need to
up grade the ignitions on these engines.I have been reading
lots of guys using the Jaguar set up.Is there a cheaper way
to go? Thats a lot of $$$$.

Flyusflg
 
After some independant testing was done, the Jaguar CDI will lose power compared to stock, and the others tested ended up about the same as stock.
There are a few in here that switched to the HD Lightning CDI who have noticed a difference in smoothness and some power gain but others have tested and compared to find the results were about the same.
I personally still use the stock CDI and hadn't ran my bike with the other CDI units yet so I can't and won't give a personal opinion on which is best. Hopefully some of the owners of the HD Lightning can chime in and give a more accurate opinion as most members who have one like it a lot.
Really, there are only 3 aftermarket ones to choose from, the Jaguar, the Rocket CDI, and the HD Lightning with the HD lightning being the most popular choice due to customer satisfaction.
Your last option would be to make your own if you got the skills to do so and a few in here have done just that and posted how they did it as well as their results. Look for the "roll your own CDI" thread in here if you're interested in making your own.
 
Thanks for the info.It,s funny for you read this & that.I just bought a kit
& have not even got it yet.I plan to tear the engine down & check tolerances.
Make sure everything is ok.I know these things from China & I know there
QC is terrible.So I,m just trying to avoid any unknown problems.

After break in I will do a little few mod,s but nothing big.

Thanks again Fly
 
I know the feeling... I never even started my engine with the stock head in place as I ordered the fred head the same day I ordered the kit... and guess what came in first...
Then when the engine came in it was off with the stock head and on with the Fred head.
Install the kit on the bike, then take the engine out, disassemble, check a few measurements, then start ramping the piston and cutting the bottom of the skirt up to increase port timing and flow.
At this point I reinstalled the engine and rode it around for a few days, it ran great but I wanted more out of it so I took the pipe off an old pocketbike and welded the expansion chamber into the exhaust system... now it's better... but then the engine started to sputter so I had to find the problem, narrowed it down to the speed carb so I ordered a CNS carb since it offers better performance...
While waiting for the new carb, the engine comes off again, this time for a full porting job as well as truing and balancing the crank, this was taking too long so I bought a second engine, installed the top end from the first, and ended up happy with the results.
So now I got a fast bike with lots of spare parts... but I'm sure there will be more upgrades as I go...
 
I have no experience with the Jaguar CDI, but if it is indeed similar to the HD Lightning CDI (witch I do run) then I can see why anyone with a "stock" engine sees a performance drop. Or, conversely, anyone with a modified engine, that has not gone very high on the compression.


From my experience with the HD Lightning CDI, it is designed to start retarding the timing as the engine reaches high RPM's.

If you build an engine with very high compression, it will start too loose power at higher RPM's with a stock CDI, as the ignition is too advanced. By retarding the ignition at higher RPM's this CDI allows the use of very high compression (in order to boost low end torque) while preserving top end run out ability.

With this CDI, I run my compression high enough to hit 240psi on a compression test, and the engine (when jetted properly) will still run out to 10,500 RPM's.

But a stock engine actually REQUIRES the extra ignition timing at higher RPM's, because its compression is (relatively) so low.


Hope that helps!


Don't hesitate to ask me anything!
 
You must log in or register to reply here.
Back
Top