CDH 110 confusion

[glebati]

I'm new to the hobby but I bought the CDH-110 engine without knowing about its flaws and now have a question.
I have watched the full video series by Build Break Fix on youtube about this engine and I was wondering how true is his claim that the engine is deeply flawed in its bottom end geometry and needs a spacer and a new crankshaft in order to be fixed properly. It seems to directly conflict with other videos on the engine where the only modification made is editing the port timing.
Also so that I have something to aim for, what should be the realistic top speed for that engine when it is properly tuned with the stock carburettor and other parts?

 

[Al Regresar]

Don’t worry about top speed (estimated probably 40 + with proper gearing). First, break the motor in properly and go for reliability.

 

[Chainlube]

I'm new to the hobby but I bought the CDH-110 engine without knowing about its flaws and now have a question.
I have watched the full video series by Build Break Fix on youtube about this engine and I was wondering how true is his claim that the engine is deeply flawed in its bottom end geometry and needs a spacer and a new crankshaft in order to be fixed properly. It seems to directly conflict with other videos on the engine where the only modification made is editing the port timing.
Also so that I have something to aim for, what should be the realistic top speed for that engine when it is properly tuned with the stock carburettor and other parts?

That guy doesn't hold too much cred around here. I bet he has a bin at home full of blown engines.

Have you had the jug off? How much side play is there in the crank?

 

[GW's Motorized]

He is correct about that engine needing alot of work, but I'm not sure if what he did is correct

 

[glebati]

That guy doesn't hold too much cred around here. I bet he has a bin at home full of blown engines.

Have you had the jug off? How much side play is there in the crank?

No side play in the crank.
However at the end you can move the conrod side to side 1.5mm and the piston side to side 10mm
And the stroke did turn out to be 37.2mm like in his video...

 

[ImpulseRocket]

The CDH110 engine BBF ha must have had a poor crank pin offset in relation to the bore centerline for the engine rotation. Or side to side alignment was off.

I have a 110 engine I bought initially to fool around with, but after investigating he ports and port timing, I came to the conclusion that it really isn't worth the effort. It CAN be a good low RPM torque monster if you want to put in the work. Aka 30mph max top speed, but will climb hills with greater ease than most.

The big issue is the iron sleeve ports are both off in alignment, smaller than the cylinder, and just generally timed terribly. The upper transfers in particular on mine were very rough and uneven. The aluminum cylinder port timing isn't much better.

That said, if you are willing to put in a bunch of work, they can be made to be decent.

On my particular cylinder I found that I needed to raise the cylinder 1.5mm to get the transfer timing to a reasonable level, but that created an issue of needing to mill almost 3mm off the top of the jug for proper squish. Then, I still had all of the port issues to deal with.

Here are a couple of pictures of the intake (at TDC) and exhaust port (at BDC) with the cylinder spaced up. Even without the spacing the exhaust port is horrible. I would have to space it up almost 6mm to get the exhaust port decent. Notice how much of the sleeve covers the port in the aluminum as well. The upper transfers are just as bad. loooooots of time with a die grinder/rotary tool is needed.





LA Hoverbikes on Youtube actually did a 2 part series on the 110 engines, with his initial run and its terrible performance, and the work he put in to make his particular engine perform decently. With a long head pipe clone MZ65 and his port work, it made so much torque down low it started slipping his clutch immediately and he had to adjust it. His carb tuning need work too so he was never really able to get it above about 26mph. He seemed fairly happy with it overall as a good low speed around town bike with lots of torque, so if you aren't after high speed adventures, it can be a good motor.

 

[ImpulseRocket]

Previously mentioned LA Hover video if you haven't seen it.

 

[glebati]

The CDH110 engine BBF ha must have had a poor crank pin offset in relation to the bore centerline for the engine rotation. Or side to side alignment was off.

I have a 110 engine I bought initially to fool around with, but after investigating he ports and port timing, I came to the conclusion that it really isn't worth the effort. It CAN be a good low RPM torque monster if you want to put in the work. Aka 30mph max top speed, but will climb hills with greater ease than most.

The big issue is the iron sleeve ports are both off in alignment, smaller than the cylinder, and just generally timed terribly. The upper transfers in particular on mine were very rough and uneven. The aluminum cylinder port timing isn't much better.

That said, if you are willing to put in a bunch of work, they can be made to be decent.

On my particular cylinder I found that I needed to raise the cylinder 1.5mm to get the transfer timing to a reasonable level, but that created an issue of needing to mill almost 3mm off the top of the jug for proper squish. Then, I still had all of the port issues to deal with.

Here are a couple of pictures of the intake (at TDC) and exhaust port (at BDC) with the cylinder spaced up. Even without the spacing the exhaust port is horrible. I would have to space it up almost 6mm to get the exhaust port decent. Notice how much of the sleeve covers the port in the aluminum as well. The upper transfers are just as bad. loooooots of time with a die grinder/rotary tool is needed.





LA Hoverbikes on Youtube actually did a 2 part series on the 110 engines, with his initial run and its terrible performance, and the work he put in to make his particular engine perform decently. With a long head pipe clone MZ65 and his port work, it made so much torque down low it started slipping his clutch immediately and he had to adjust it. His carb tuning need work too so he was never really able to get it above about 26mph. He seemed fairly happy with it overall as a good low speed around town bike with lots of torque, so if you aren't after high speed adventures, it can be a good motor.

I am a little confused about raising the cylinder in order to improve the transfer ports' timing
Moving up the cylinder would have the same effect as dremeling the top of the transfer ports right? (increase duration) So could I just do that? Or would that leave too little material on the top of them and risk it blowing up? I think LA hover bikes just dremeled them too.

 

[GW's Motorized]

Port timing includes the bottom of the port

 

[ImpulseRocket]

I am a little confused about raising the cylinder in order to improve the transfer ports' timing
Moving up the cylinder would have the same effect as dremeling the top of the transfer ports right? (increase duration) So could I just do that? Or would that leave too little material on the top of them and risk it blowing up? I think LA hover bikes just dremeled them too.

There is port timing (when a port opens and closes) as well as port duration (how long its open for) combined with the timing in relation to another port, I.e. Blowdown, or the degrees between when the transfers open to when the exhaust opens. Then there are other factors, such as crown height vs. port floor height on the exhaust, and skirt height at TDC vs. the port roof on the intake.

Sometimes raising or lowering the whole jug can allow for a compromise/balance between all of those factors. In the case of my 110 cylinder, the intake, aside from the sleeve protrusion, was decent enough that I could raise it to compensate for the exhaust port being too low for the crown height and for timing overall as well as my transfers being too low and very very short duration. Once raised I could lower the intake floor and raise the exhaust roof to get the timing numbers I needed, and with the upper transfer ports it allowed me a lot of room to set them however I wanted since I had a big lip from the sleeve. I could then go in and fill the roof of the upper transfers with epoxy to get a perfectly perpendicular roof, as well as put in an angle on the edges to try and direct the flow to the intake side.