Resto Mod for my 71 CT70

Carlo C.

Active Member
Merry Christmas everyone. After 2 weeks of waiting I finally got what I thought was all the jets for my carb, but quickly realized that the Pilot jets I ordered were wrong. If any of you guys know which jets I need I would greatly appreciate the help.

The Pilot Jet on the left is the one out of my carb (L38) the one on the right is the one that came in:
Pilot.jpg


Pilot L38.jpg



This is the carb it had a 95 main jet:
Carb (1).jpg


Thanks
Carlo C.
 
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Carlo C.

Active Member


kirrbby,
They don't have them that I could find, but dirtbkr188 found them for me on a site called www.jetsrus.com they are for a Keihin 3J and only come in 3 sizes 38 is the smallest then 40 & 42. I ordered the 40 & 42. https://www.jetsrus.com/a_jets_by_carburetor_type/jets_keihin_3J_slow.html

Merry Christmas
CT70 (101).jpg

Thanks
Carlo C.
 
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OLD CT

Well-Known Member
Sorry to hear that. This is the jet that fits in my carb, but it is ten years old. The knockoff vm22's have changed since then I guess. I bought my jets from niche quite a while back. Here is the one that fits my knockoff vm series carb. It's actually a genuine mikuni style jet, and it fits in the old knockoffs.
 

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Carlo C.

Active Member
Sorry to hear that. This is the jet that fits in my carb, but it is ten years old. The knockoff vm22's have changed since then I guess. I bought my jets from niche quite a while back. Here is the one that fits my knockoff vm series carb. It's actually a genuine mikuni style jet, and it fits in the old knockoffs.
OLD CT,
The one in your picture is the same ones that I got in. They don't fit this particular carb which I am assuming is a knock off of a knock off. At least with some help I found the correct ones. Hopefully this will at least get me in the tuning window for this engine with this carb. This takes the fun out of the bike for sure.

Carlo C.
 

Carlo C.

Active Member
Guys,
Still waiting on a couple jets to come in to put the 22mm carb on the bike, but I did get the extended adjustable air fuel mixture screw for the carb that Tim told me about. I really like it and it makes it really easy to adjust even with the carb on the bike.

Carb Screw.jpg

I also received my new VIN tag. I took a chance and ordered it off of ebay and it is really a nice piece. It is done on aluminum just like the original and was engraved with my VIN before they shipped it. I am thoroughly impressed with the quality. I bought some of the factory rivets from a guy on ebay about 10 years ago and have held onto them like gold. I think it came out great and just adds a nice touch to the bike.

Vin Tag.jpg

I am gonna order the front disc brake kit from web bike Japan. I will have to take it apart have the hub powder coated black, add the delrin bushings and the correct rubber fork boots so it looks correct then I think I am done adding stuff to the bike for a while and I am just gonna go riding and enjoy it.
Front disc conversion.jpg


Carlo C.
 

Carlo C.

Active Member
Guys,
I have to give a big shout out to Tim "dirtbkr188". I have been fighting with this cheap Mikuni knock off carb that I bought of amazon after watching a video with a guy speaking very highly of them. It ran like crap when I put it on the bike and Old CT, kirrbby and some of the guys helped me out finding jets to fix my problem. Well when all the jets showed up they were wrong. It turns out this carb is a copy of a copy and the jets are for a Keihin style carb and were hard to find. I ordered them and waited another week for them to come in and once I got them they still did not solve the problem. I even bought the billet long air idle screw so I could tune with the carb on the bike. even with the biggest pilot jet I have it was still really lean off idle and just would not cooperate. Tim and I were talking back and fourth and he told me he had a older version of this carb stored away somewhere and when he put his hands on it he would send it to me to try. Well I got it in yesterday afternoon put it on the bike and it was about 85-90% better then the one I bought. It just had a slight stumble and crappy run right off of idle. I knew it was lean, because if i just touched the choke a tiny bit it would clear up. So since I now have jets for all the versions of these carbs, LOL I decided to change the pilot and see if it would fix the old girl. I took it apart and it had a 20 pilot 105 main and needle was set in the middle. I messaged Tim just to make sure we were on the same page and he agreed and said change the pilot and use your long air/fuel screw so you can adjust easily. I made all the changes and even reset the float level. The bike started on the first kick without the choke and runs absolutely perfect. Idles great has perfect off idle throttle and runs great at wide open. I cant thank Tim enough as he has just been a huge help as I would still be fighting this thing without him.

Mikuni 22.jpg


So the engine is a Lifan 125 the carb is a Mikuni 22 old school that actually says Mikuni Japan T/A on the side. It has a 105 Main Jet, 22.5 Pilot Jet, Needle is set in the middle and air/fuel needle is at 1-3/4 turns. It has the cheap china exhaust with 8 holes drilled in the baffle. This could be a good starting point for anyone with the same combo.


Carlo C.
 
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OLD CT

Well-Known Member
I had a feeling 22.5-105 would do it. Good on you for not giving up and Tim for parting with the old school version. They perform nice.
 

Carlo C.

Active Member
I had a feeling 22.5-105 would do it. Good on you for not giving up and Tim for parting with the old school version. They perform nice.
OLD CT,
Thanks for all you guys help with this you made it easy other then the waiting. I am gonna order a few new spark plugs, what do you guys recommend? I want to do a few wide open runs and check the plug to make sure we are on the money. I might wait to do that as I plan on changing the exhaust to this one from Bart Moto https://bartmotoco.com/products/k0-style-big-bore-exhaust .

I did take the old girl on a pretty decent ride to the auto parts store. A few of the guys came out from behind the counter to check it out. One of them asked me if it was real Honda or a clone? I must have made a face :mad: when I answered and said it is a real 71 Honda. He said sorry don't take it the wrong way it is so clean and nice it looks brand new. I laughed and said no problem and thank you I just finished re-doing the entire bike. :)

Carlo C.
 

Carlo C.

Active Member
Guys,
I finally took the old girl out for some speed runs. I put a new NGK plug in went for a little ride to my test spot and then let it rip. I did not tuck down or anything crazy and it went 54mph topped out. I let it cool down a little while and put another new plug in and made a another good run and it again went 54mph. I pulled in the clutch shut it off coasted to a stop and pulled the plug. The plug showed to be a little bit on the fat side so I was wondering what you guys thought about a main jet change? We have really good weather here today 53 degrees and dry so I am thinking when we get our normal hot and muggy New Orleans weather it is gonna really be on the fat side. It has a 105 main jet in it so just looking for ideas on how big of a step down to make?????

I am 6ft tall at 230lbs bike has a 17/35 gear combo with 120/90-10 tires. I think the bike runs great for what it is, my goal was 50mph and it surpassed that so I am pretty happy with the performance so far. I just want to make sure it is tuned properly. Let me know what you guys think? The speedo on the bike is a little off it showed around 47mph when I glimpsed at it while the GPS speedo on my phone showed 54. I could be off on the bike speedo numbers a little also as I really wasn't trying to look at both and ride.
:red70:

plugs.jpg Phone Speedo.jpg

Carlo C.
 
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Carlo C.

Active Member
Guys,
Have to give a thanks again to Tim "dirtbkr188" he helped me out with some more information about these carbs and let me know that JetsRus does have a #102.5 main jet. I think that will be perfect and a much better smaller step then the #100 Jet I have here. My thoughts were that even though it is running good right now, I think once our typical hot and muggy weather hits the New Orleans area the #105 may just be a tad too much and that #102.5 will work out perfect. I will order it and make the swap It's easy enough to test and if its not better I will just swap back.

Carlo C.
 

Carlo C.

Active Member
Guys,
When I decided to finally build this bike and got it out of my back storage shed where it had sat on top of a crate of parts I had been collecting for a long time, I had a hard time figuring out what it actually was. The date said 8/71 and it had a 7 digit vin and the two holes for a helmet lock that makes it a K1 which seemed pretty easy right? Well the front forks on the bike were K0 and it had a cracked K0 1 piece aluminum triple clamp. It would take a lot to make me believe that any of it had ever been off or changed before I pulled it apart. The color was exact with the same patina on Frame, forks and what was left of the K0 headlight bucket. When I disassembled it the old grease and ball bearings all seemed to be original and even the nut on the stem did not have any of the usual marks like it had ever been removed. It also had a plastic K0 gas tank and the correct K0 short tank mount and I could be wrong, but it all seemed like it had never been removed from the bike. There was no impression on the frames original paint from where the tank mount stopped and the seat bracket started. I am still a little baffled with all of that and honestly have no answers for why it was that way. None of it really matters to me as I never intended to do a concourse correct restoration on this bike anyway. Just figured I would share that as someone may have some answers.
Frame.jpg


Anyway, the short tank mount for the plastic tank that was originally on the frame had some rust pits on the top of it that were deep and made me not want to use it. I had a really nice like new steel tank mount so I used it during the build with the a new rubber for the plastic tank. It worked, I just did not like the little bit of slop it left where the filler neck came through. I have been looking for another K0 tank mount for the plastic tank in good shape and found one on Ebay for a decent deal. I ordered it and It came in yesterday so blasted it and sent it off to be powder coated. I don't know why my K1 frame had all of these K0 parts on it, but I am gonna put them back like it was.


Blasted
Tank Mount K0 2.jpg Tank Mount K0 1.jpg

Powder coated semi gloss black
Tank Mount K0 3.jpg Tank Mount K0 4.jpg



Carlo C.
 
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JHminitrails

Active Member
Early K1 bikes had plastic tanks. The VIN break was at CT70-2040050 according to the parts catalog of the day. Bikes built after that have metal tanks. I have 2 early K1 bikes here that both came with plastic tanks. There is also 2 versions of the "long tank brackets", one has a larger hole for the metal tank, which also uses a different rubber isolation ring. Your bike frame was definitely was born as a early K1. Pics added to show the difference in hole diameter. Smaller hole is for early K1's with plastic tanks. Hope this helps anyone who is wondering.
 

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Carlo C.

Active Member
Early K1 bikes had plastic tanks. The VIN break was at CT70-2040050 according to the parts catalog of the day. Bikes built after that have metal tanks. I have 2 early K1 bikes here that both came with plastic tanks. There is also 2 versions of the "long tank brackets", one has a larger hole for the metal tank, which also uses a different rubber isolation ring. Your bike frame was definitely was born as a early K1. Pics added to show the difference in hole diameter. Smaller hole is for early K1's with plastic tanks. Hope this helps anyone who is wondering.
JHminitrails,
You are correct according to the vin number cutoff you posted. My bike starts off with 200 so it seems to be a very early K1 and that explains some of the crazy mix of parts on my bike. I still cant explain the K0 forks, Headlight bucket or Triple clamp. Maybe my bike got thrown some leftover parts in the mix who knows?? Thanks for the really cool information.

Carlo C.
 
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Carlo C.

Active Member
Guys,
I have a technical wiring question for you guys. I will try to give you guys as much information as I can. Without the engine running when I turn my key on the ignition switch to run in the first setting the running light on my rear break light and horn come on and work fine, When I turn the ignition switch to the second setting without the engine running nothing changes. With engine running the ignition switch in the second setting the headlight, running light in the speedometer, the neutral light and high/low beam then all work as long as the engine is running. I believe this is all correct.

I have a 12v half wave Regulator/Rectifier from T-bolt installed on the bike and it seems to be at least partially working, when I start the bike my headlight and other lights come on work fine and have not blown. The problem I am having is that my battery is not staying charged. I have not put a meter on anything yet, but obviously it is not sending the trickle charge from the regulator/Rectifier to the battery to keep it charged. If I manually charge the battery (New) it will last about a week before it gets low. I am wondering if I do not have the correct Regulator/Rectifier on the bike or I just may possibly have a bad one. I don't know if my engine is a half wave or full wave. I do know it has two yellow wires coming out from the stators and I wired it according to information I found on the T-bolt website which said to just ground one of the yellow wires and run the other one to the Regulator/Rectifier. I have the red wire from the Regulator/Rectifier going to the positive side of the battery to keep it charged. Let me know what you guys think?

It is wired like this:
YELLOW-Connection-YX-reg-11 (1).jpeg



Carlo C.
 
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kirrbby

Well-Known Member
Bolt shows that diagram for yx engines with SINGLE yellow feed. But I think you have to use their other diagram that shows 2 yellows from the engine.

You are using a stock type wire harness which is made to use 2 separate lighting circuits. And you are trying to make it work with only ONE lighting feed.

It helped me a lot when I learned that the reg/rec is basically 2 separate gadgets in one package.

One gadget only regulates AC power. We use that to run our headlight circuit.

The other gadget only changes AC power to DC power...rectifies it to DC..?
We use that only for our battery circuit.

I think the problem lies somewhere in there... You are sending one lighting circuit into both gadgets...and...you are using a wire harness that designed to have 2 different lighting circuits.

But...tbolt is showing a diagram...and mentions it's for CT70s...
 

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kirrbby

Well-Known Member
That diagram is showing a white wire too tho..? I don't think there IS a white wire from your stator? Do you have 2 yellows AND a white?

I'm thinkin that your stator is the full wave type. And may be best to set your bike up for full wave...one lighting circuit...all battery power.
Or...swap the stator to a half wave type. Then, the stock wire harness can work as it's designed to work...2 separate circuits.
 

Carlo C.

Active Member
Guy's
So after doing a lot of reading (Thanks kirrbby) and research I think that just have a bad regulator/rectifier. I have to remove the engine to change it, but I have a new one to try. I am very very picky about wiring and I even have a separate huge Snap on Tool Box at my shop just for wiring and wiring tools, so I was a little disappointed that my battery was not staying charged. I was second guessing everything I did when I built the Harness.

Here is what I have come up with so far:
I have a 125 Lifan with 2 yellow wire system.
2 yellow grounded.jpg
According to everything I have read you are required to ground 1 Yellow wire and send the other to both AC inputs on reg/rec. This then turns the system into a single wire grounded system.
2 Yellow Output.jpg RegRec AC Input.jpg
The reg/rec should then regulate the voltage for the headlight and other bulbs so that it does not send a over voltage and pop bulbs. (This is working correctly).
The reg/rec should also rectify the AC voltage it to DC and trickle charge the battery. (This is not working)

Single Yellow Feed.jpg

So in my opinion I feel that since the single yellow wire is putting out voltage and that regulator side of the reg/rec is working that there is just a problem with the rectifier side of the unit. I just cant find anything else that would be a problem.

This is exactly how my bike is wired with the exception of the electric starter
Pardue 2.jpg


I guess sometime this week I will get it apart and swap the reg/rec and hopefully then it will work and keep my battery charged

Carlo C.
 

kirrbby

Well-Known Member
Man... IDK Carlo. Some of the wire diagrams...well I'm sure they work if you build everything from scratch...with a plan for success. But if you use any of the original wire harness, and or key switch...I think you'll have to think it all thru. That stuff is designed for the 2 separate circuits...one being battery power DC...and one being AC straight from the stator.

From what I THINK you have planned...
I'm thinking you will be, REGULATING AC down to 12v, BEFORE you send it to a half wave RECTIFIER. The half wave rectifier will waste ½ of your available current. So you'll want to power up SOME lights with AC. And some with DC...same as Honda did. AC will only work when the engine is running...same as stock.

Splitting a single circuit into 2, means you still have only one circuit. So it seems it would be tricky to split it into 2...one AC and one DC. But...I don't fully understand electricity...so I'm not sure if it's even a worry at all.

I guess my biggest concern... Why wouldn't Honda have done it this way?? They split the stator into TWO lighting circuits, with a half wave rectifier and battery on ONE of them. They did it on the 6 AND 12v setups.
On the CL70...I think they used only one DC circuit for all...but it has a full wave rectifier...I think. Lol

I'm sorry if I'm just complicating things...adding confusion.
When it comes to our electricals...I do that to myself a lot :confused:
 
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