CT110 Performance/Gearing?

[RadRacer203]

Still testing out my 1984 CT110 and it seems like it's working perfectly. The only problem I have with it is it's a bit slow. At maximum rpm, it seems to only go about 50 or so on flat ground. The carb is a rebuilt OEM one, everything on the bike as far as the engine is concerned is either original or a stock replacement as far as I know (haven't checked the front sprocket size yet). I was just wondering if there might be any way to squeeze out a bit more power. I'd ideally like to make it able to go 60 flat out so I can cruise at 50 mph and not be on the redline. I've heard fitting a 16 tooth front sprocket will help so I'm going to probably do that. Just wondering if anyone has any suggestions, like some tweaks I can make. I was also thinking of fitting a larger rear tire when the one on it wears out

 

[fatcaaat]

Hi. For the 110 there are virtually no options available...slightly an odd duck compared to the CT90 and 125m...the cams and cylinders are not directly interchangable. As for your sprocket, there are only 14 and 15 tooth front sprockets available as no one ever made any other sizes for them. Your desire to achieve a 60mph top speed with 50mph is unattainable without major mods. I have owned, modified, and worked 3 different CT110s and the best I was able to achieve was about 57mph on the flat and comfortable cruising at about 47-48mph.

If the bike is running perfectly, you can drop the rear sprocket by 3 teeth. DOn't do 4, it won't pull it. Doing this will also result in you needing to downshift up small inclines that you previously crested in 4th gear. The biggest impact to the power and top speed of the bike was putting a PZ19 carb on it. Yes, they are Chinese, but that carb ran the bike better than the rebuilds I did on the stock carb as the stocker is only a 17mm.

I had done enough research to send a camshaft to webcamshafts.com for a grind, but I didn't think it was worth it. You are trying to get blood from a stone with a CT110...simply not the best platform to build from. Another option is to do a larger overbore with the rear sprocket reduction. The CT110 has a lot of meat on it. The ATC125m, if you mill it short will work as well since it's all steel with no liner in it. I don't remember if you'd need to bore the engine cases out or not with the 125m shortened cylinder, but fairly certain you can punch it to 60mm if you can find a piston for it.

Lastly, you can go down the path a friend of mine has...take the 110 engine out and replace it with an ATC125m. YOu can remove the pull start from it and make a cover, use the electric start and if you break the cases, you can pop a kickstart in there as well. YOu get 12v power and honda reliability. Unfortunately you will do all of that, and just, and I mean just reach your goal, once you port that head and pop on a mikuni VM22 carb...a real mikuni here, not the chinese carb branded VM22.

 

[RadRacer203]

Thanks for the reply, I definitely don't want to go crazy with it, although I might put a 125m engine on it if/when this motor blows up. I guess I definitely can't get to a top speed of 60, but maybe I can change sprockets around and get the rpm's down a bit at the top end.

My ignition system is working as it should, I think the timing is good, the carb is freshly rebuilt, and running well, maybe a tad rich but not enough to worry about. I'm mainly wondering why I can only get to 50 at the redline? The quoted top speed is 55 so I'm wondering where those last 5 mph went, cause it's a very clean, low mile bike that's running nicely. The one thing I haven't checked is the front sprocket to see if it's 14 or 15 tooth, but I'm just trying to figure out how to get to it and what gaskets I need to buy when I open up that side of the engine.

I'm thinking I may get the performance cam from dr atv and install it over the winter too, looks like it would increase midrange performance. Would be nice for climbing hills at speed for sure

 

[Old Guy Too Many Bikes]

My neighbor has an '83 CT110, and it's was good for about 50 on flat ground same as yours. He weighs 230 lb. However, at those speeds, the engine and drivetrain is pretty noisy and busy, even at 40 compared with a CL90. I think those extra gears and friction due to the dual range trans cost ya. We installed a 40 tooth rear sprocket and it improved things quite a bit. It won't do 50 any more, but at 40-45 the bike is quieter and cruising is much more pleasant. Yes you have to downshift on hills and such, but it's a small price to pay. Also, installing a set of street tires makes the bike ride smoother and the steering lighter and more precise. If speed is your goal, drop a YX140 in it and you can cruise at 55 and top out at 65.

 

[-Nate]

" I think the timing is good,"

-Can't be any 'think' about it, the timing is critical and must be set to the "F" mark , not the "T" mark .

Valves *must* bet set when stone cold to .002" .

The ports, intake and exhaust are smaller on the CT110 so it will never breathe as well at higher speeds, there's a trade off there .

 

[RadRacer203]

Ok, so I'm definitely going to be on the lookout for an ATC 125m bottom end to build, but I've been doing some thinking about this. I took my bike on a top speed run and it seemed to top out at about 45 at full throttle on flat ground. I haven't gotten a look at the engine sprocket yet but it seems to me like someone could have possibly put on a 14 tooth one instead of the stock 15 tooth, and just doing some rough estimations on an online calculator, it seems like that would cause the top speed to be ~45 ish rather than ~50 ish. I have not checked the timing yet but I think I should. It runs very nicely but someone had definitely been in the engine before, at least with the clutch cause the clutch was assembled wrong when I bought the bike and it wouldn't shift. I'll be looking into it over the winter for sure

 

[The Flannel Flyer]

Super late reply here, but I ditched the the stock 45 tooth in favor of a 42 tooth from JT sprockets on my '81 model with points ignition, and now top out around 53-55mph in a tuck; and it can also comfortably cruise in the upper forties without sounding like it's about to float valves or explode. I found that refurbishing the spark advancer and drenching it in assembly lube made the biggest difference for me. a sticky spark advancer can easily make the bike sluggish no matter the gearing. Because I took the time to do the spark advancer, I felt little to no loss in acceleration despite the higher gearing, but long hills were, and still are a bit of a struggle in 4th gear.

 

[b52bombardier1]

You did good, young CT rider and have improved things for speed about as much as possible. I changed the size of the rear wheel on my Honda CL100 by one inch for about the same results.

Much more than this amount of chasing higher performance on these bikes is simply moving the deck chairs around on the Titanic . . . not much point to it.

Rick