MC 54 250B valve adjust and carb idle problems By bobf (Read 2,353 times)

[bobf]

No responses but for the price, it is much cheaper than a valve job. So I ordered one today. Maybe a week and then I can report on the activity with the new 'intake manifold'. Sure hoping for some good results.

Edit to add: Monday 2 Nov, I received a email saying my package had been sent. Good start.

Edit to add: Wednesday 4 Nov. I received my new part in the US mail.

May have time to work on the scoot Thurs or Fri. Will report my success or failure when done.

[bobf]

Did get new intake manifold attached to the engine and then installed the carb again. Could barely get the air tube installed poorly. Tried to run the engine but it ran lousy. I just could not get the air tube installed. So I looked up a new one for about $12 and ordered it. The measurement on my old one was below the spec and the flexible material had pretty much hardened. Maybe by Tuesday I will have my new one.

Browsed the web today and found a place to download a Honda manual for the engine in my machine. For $10 I downloaded it and have read some and printed what I thought would be helpful. My engine runs erratic and backfires. I saw in a couple help items that back firing can be part of the air system leaking. So maybe I am on the right path again. Another problem might be in my electrical timing system. Sounds like more parts if so. I will continue on the mechanical side first.

They also tell of how to find Top Dead Center. I looked at my engine and sure enough where they said to look I finally found the access hole, with a shiny screw out plug in it. It means I must take the outer drive cover off to be able to turn the engine till the marks are aligned.

When that happens I will set the valves with the engine cold. Set the valves and mark the curved part of the adjuster thing where it should be. I have tried the engine running method but poor luck as the tapping is hard for me to hear and the screws just keep spinning. So I would attempt to adjust then shut down, try to hold the arm in position then tighten the screws. Just a poor thing for me to do and be accurate at all. It seems like a three handed job

At least now with the book I feel I have an advantage to getting the thing running again.
..........................
10 Nov just got an email today saying the part shipped. Possibly delivered 17 Nov.

[cyborg]

good luck,,,you'll get it now with the manual,,,

[bobf]

Yesterday, 12 Nov 2015, my new air tube arrived in the mail. I have already reset the valves cold, restarted the engine, after setting the valves. It ran briefly so I am sure the valves are set OK. I have now got a black mark on the top of the adjuster parts so I should be able to get back close to the set place if they do get moved. Hope to get the air tube installed today but may have to wait till tomorrow.

[bobf]

I need help for ordering parts. I have the water cooled Honda clone and am looking at possible parts to order. I see two parts side by side at the vendors. One is described as for the 250 engine and the other is for the 250 engine and they describe it as for a 172MM.

Sometimes I see the 172MM in posts here and now in catalogs for parts. Just what does 172MM mean. I hope it is for the water cooled Honda Helix clone that I have.

A 6 pin CDI for $9.95. Have not tested it yet but it comes up a lot in the 'Trouble shooting list'.

[ellpee]

In simple terms, the CDI sends a spark to your plug, or rather, tells your coil when to do so. If the engine starts and runs, even badly, a faulty CDI would be low on my suspect list.

As to your part question, what the heck part are you talking about? No mind readers on this forum far as I know.

[bobf]

Thanks for your post ellpee. You are right, I am looking for the wrong part. I should be looking for the Ignition Control Module the ICM according to the trouble shooting charts. So back to work again and seeing if I can find and test it.

My question was actually about the term 172MM. Does this mean the water cooled Honda we have in our scoots, or something else? In your case in your previous scoot.

[ellpee]

Little bit of guesswork here (JR, where are you?), but thinking 172mm has to do with the diameter of the air intake or mixture outtake of the carburetor. Are you now toying with replacing the entire carb? Thought you did that already ....

[bobf]

As far as I am concerned I am done with the air system and the carb. Just replaced the air system from behind the carb and before the carb. Replaced the carb and it got worse so I put the original carb back in. I followed the wires and reset connections till the replaced temp senders actually started running the fan. Now I have a Honda Helix engine manual, something that many say is the engine in our scoots, that I am following. So I have redone the valves with the Honda technique of cold and set by hand. It seemed more secure to me than while running and listening for tapping. On my engine the clamping bolts were spinning and looked like they might just spin off while listening for tapping starting or ending. It was a three handed job. Cold setting was good on my engine. Move the arm till you feel resistance. Then set a half mark back to loose directions and lock it down. That is supposed to be the .04 setting;

Now I find disagreements in the manual and some descriptions in the market place that do not match. One being the Ignition Control Module in the Honda manual that are 6 connector boxes working to help control the spark but in the markets they are called 6 pin CDI for a 172MM scooter. The descriptions and pictures look the same but names are different. So my question about what is a 172 MM scooter.

I am pretty much done with mechanical solutions right now, but for damaged valves and a valve job.

I was hoping for a low cost electrical solution and the Ignition Control Module($10) and the Ignition Pulse Generator come up often in the trouble shooter charts. And often in likely hood positions of 1 and 2. I have not tested them yet as described in the Honda guide, will do when again I have time to work on my scoot. I was just looking for availability and cost. Satisfied that cost is not much. I found sets, not matching my scoot for CDI, Pulse Generator, and what looked like connecting to plug wire, for about $35 - $45. These were for the lower powered scoots like 50cc or 150cc. Not sure for the 250cc. Still reading and trying to test, Honda suggest a resistance check and gives numbers to look for, and decide which way to go.

You commented that you did not see the CDI as the problem. So once again can you give me a good hint at what to look for? One area suggest poor connections at the ignitions switch and other places. I think I have already done that but maybe another look again won't hurt. It was something that came on quickly and I just can't seem to find it successfully. I think the overheat and fan is fixed. The air system is new and hopefully fixed. Your next best suggestion will be looked at.

But for lack of experience I will try to follow the Honda trouble shooter list that makes sense to me. If I could get it running enough to drive to a motorcycle scooter repair place, not sure we have one here in Casa Grande, I would take it to them for some help. Otherwise the end will be a low price and on the curb.

[ellpee]

No, no suggestions, unfortunately. I ***THINK*** the CDI and the "Ignition Control Module" may be the same, just different names; the gizmo that somehow tells the coil (Ignition Pulse Generator?), based on engine rpm or whatever, when it's time to shoot a high-voltage pulse to the spark plug. And it seems to me if your scooter runs at all, neither of those items is likely to be faulty. Others here may correct me on that.

To be honest, I at least have lost track of what the problem is you're trying to fix. You got your valves set to your own satisfaction, everything in the fuel/air path from air cleaner all the way to cylinder head checks out, original fan problem way back when seems to be solved, so what's left that you're trying to fix?

[bobf]

I am trying to get past starting, poor idle control, and stopping. Just not running well at all. Idle will start but then run faster, then slower, then faster, then stop. Sometimes it may backfire, but other time not. Can't seem to get beyond a minute or two of running but when I stay on the throttle and adjust to keep it going, I get enough time to warm the head a bit. Some carb adjustment coming further down the list of the Honda guide.

I just want to have time to do the resistance checks suggested before I start doing the carb adjustments. I am going to take the wife shopping to day and while in WalMart I hope to find SeaFoam for the gas tank. A person from Texas suggested that as a help in cleaning the carb. Worth a try before fiddling with carb adjustments.

Thanks for your inputs ellpee.

[ellpee]

There's a place called Scoot Over Tucson on Broadway Blvd in Tucson that will -- reluctantly -- work on Chinese scooters as long as it doesn't involve tearing into the engine or similar. I've used them twice, and got a square deal other than the "we won't get into the guts of anything Chinese" thing. (They sell Taiwanese Kymco scooters.) You can rent a U-Haul motorcycle trailer for about $30, bring your scooter down here, and let them deal with it. Another $30 for the trip back home to Casa Grande. With all you have going on with your wife, it might be time for you to pay the piper and let somebody else sort out your scooter problems. Seems like the more you dig, the deeper you get.

[bobf]

Thanks ellpee. You are right. Today again I go to the hospital for the wife's blood test. Then this afternoon to her heart doctors.

If the guy in Tucson won't go into the engine, then he won't like me. There are scoot shops up in Phoenix that do sell these scoots. So if necessary I could go to them. And Phoenix is closer than Tucson, I think. Also looking for a Honda dealer that may work on the engine if I give him a stripped down scoot. For a valve job I wonder if I could just pull the top off the engine and take it to a machine shop, like the Honda dealer. Something to look into if that is where I end up. Just need the valves and a gasket set to get that done and rebuilt.

I just put some SeaFoam in my scoot tank. But won't get to work on it today. Maybe tomorrow. I need to do those resistance checks to get beyond the electronics. Then move on down the list.

[bobf]

Today I had time to work on my scoot. Not much but I checked the Ohm's on the cable of the starting enrichment (SE) thermal valve.

The Honda manual says it is to be 10 ohm/s. If the reading is not within the limit, replace the SE thermal valve. On mine it read at about 7 ohm. Does this mean to replace the thermal valve ? Within the limit is a bit vague. Does it need 10 ohm or above or 10 ohm exact or 10 ohm or less.

Then I started the engine, forgetting that I had disconnected the thermal valve cable. It started and ran, roughly. It would drop down to about a 1000 rpm or less then idle at about 2000 rpm then drop down and go back up and sometimes it would rise up to about 3000 rmp then drop down again. This went on for quite a bit of time. Enough to get the head too hot to touch. Then it quite.

So I hooked up the cables and tried it again. It started and ran. But not for long as it would just shut down. Restart and run for a few seconds and then shut down again.

I am not sure if what I have found is a clue to all the start and run problems or not.

Any advice would be appreciated.

[bobf]

I don't know yet what is wrong with my engine. It still varies between a choppy idle and high end roar. Up and down and up and down and finally a coughing choke to quiet.

I just ordered a CDI for my scoot. I compared my order to the one being offered for $9.95 and $4.95 shipping. Probably late next week due to Easter time for many.

Recvd email: Order was packaged and mailed UPS on Wed evening.