Newbie looking for some advice

mfc392

New Member
Picked up a 1978 model trail 70 last week. I have been trying to get it running and was hoping I could get some input on what to do. Basically 22 y/o with limited tools/knowledge etc... SO here are issues I know of so far and what I have done myself in attempt to get it running.

Changed oil
Changed air filter
Cleaned carb (probably needs more adjustment) maybe rebuild kit
New Battery
New fuel
**New spark plug** The spark plug hole was pretty stripped when I got the bike. I read I could retap to a 12mm size as I figured that might be the easiest fix so I did. Went from the C7HSA to the D8HA that I believe is used in the CT90s.

Was able to bump start it the other day but it did not stay running so I'm assuming it was either air/fuel...
I haven't been able to set points and look at the condenser and set cam timing because the screws on the flywheel cover are so stripped. Again I do not have the tools at my disposal right now to remove them.

Tried starting 2 days ago, no spark/compression. Pretty bummed about it haha. Read might need top end rebuild/valve adjustment?

Didn't wanna have to take it in and spend a bunch of $ on it, but I also do not wanna screw anything else up.

So with all that said, should I attempt to do what I can myself and then let Honda take a look at her...?
 

b52bombardier1

Well-Known Member
Often, a Honda dealership will not touch these bikes because of the points ignition. If it is not a CDI ignition, they might not touch it.

We can certainly help you. Though I would suggest examining the D8HA plug and hope that the tip electrode is not deformed for being too long. Hopefully, it's heat range should be satisfactory as well.

Definitely check the compression and download a shop manual. Yes, on checking the valve lash and it's easy with the correct tools.

Rick

Two CT90 and two ST90 bikes
 

mfc392

New Member
I talked to the guys at the local dealership and they will work on it. I mentioned the spark plug issue and he gave me a few options such as putting an insert in for the correct spark plug, which I would probably prefer. He also mentioned replacing that area as a whole and that seems more expensive. I'm thinking about ordering new parts and then just have them put them in. I'll download a shop manual and check that out. One of my questions I have is what order would be the best in diagnosing the problems (if that makes sense). Super anxious to get this bike going again, I just need some patience lol. I'm located in Chico, CA.
 

69ST

Well-Known Member
Welcome aboard:wave:

Some brick & mortar shops can do first-rate work. Unfortunately, 21st century reality is that most dealerships are primarily in the business of selling financing and consider anything more than 2 years old to be "ancient". Fortunately, that's not across-the-board. The mere fact that they said they'll work on your bike is a positive sign.

Still, there's no substitute for self-reliance and the skills needed to do most of the tasks that can keep one of these bikes going indefinitely can be learned. Sounds like you have some mechanical experience, enough of a foundation to begin what will hopefully be, a satisfying process. These bikes, being of an earlier era, are decidedly DIY-friendly.

FWIW, I agree that repairing damaged plug threads with a proper insert (Helicoil or Timesert) is the preferred method.

Based on what you've posted, thus far, the carb needs to be cleaned & rebuilt (fairly straightforward and not much money) and the top end needs to be inspected. Compression loss means leakage past the rings and/or valves. If the motor had compression when you started off, then either something is prevent the valves from seating fully, or the cylinder has become scored. If it were mine, I'd pull the cylinder head, expecting to do a valve job. While it's off, you'll know instantly if the cylinder walls are scored/rusted. Tapping the plug threads, with head in place, could be the root of compression loss.

For the short-term, I'd concentrate on the carb and ignition. It'll never run without proper fuel & spark. If it's got decent spark, you can delay the dealing with the points & condenser until you've sorted through everything else.
 

mfc392

New Member
Bought a whole new carb, points/condensor, ignition coil (noticed that the wiring was not connected to where the plug portion goes into... there a quick fix for that?) Another question I have is can I pull the cylinder head off w/o taking apart the bike? Could valve adjustment be an easy fix for compression or will I need new pistons/rings etc..? Hope this makes sense LOL:42:
 

cjpayne

Well-Known Member
Bought a whole new carb, points/condensor, ignition coil (noticed that the wiring was not connected to where the plug portion goes into... there a quick fix for that?) Another question I have is can I pull the cylinder head off w/o taking apart the bike? Could valve adjustment be an easy fix for compression or will I need new pistons/rings etc..? Hope this makes sense LOL:42:
1. Be careful installing the intake to the head. The threads will easily strip out. Set the points @.016. Get GOOD at soldering before installing the condensor(it probably doesn't need a condensor), no room for sloppyness there.lol
2. Post a picture of the plug portion.
3. Yes the head can be pulled. Get a Clymers/service manual.
4. Someone else here will have to advise about the head. You will need a compression tester. Taking the head apart is the only way I know to get the best visual of head/cylinder condition.
5. DON"T be nervous.lol. Just be willing to learn, patient, and we'll get you through it.:16:
 
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OLD CT

Well-Known Member
Changed oil
Changed air filter
Cleaned carb (probably needs more adjustment) maybe rebuild kit
New Battery
New fuel

Here's something worth mentioning. It's important that you use motorcycle specific oil,not just any oil on the shelf at the parts store. These little bikes need wet clutch friendly JASO rated oil!
 
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b52bombardier1

Well-Known Member
Definite plus 1 on the oil suggestion. Stay away from any oil that say's "Energy Conserving" or "Resource Conserving" on the jug. These oils have friction modifiers that can ruin the fiber disks in our clutch packs. JASO MA rated, as suggested. Honda GN4 or Shell Rotella T or T6 works well and the Rotella is usually in stock at Walmart for fairly cheap.

Rick
 
Bought a whole new carb, points/condensor, ignition coil (noticed that the wiring was not connected to where the plug portion goes into... there a quick fix for that?) Another question I have is can I pull the cylinder head off w/o taking apart the bike? Could valve adjustment be an easy fix for compression or will I need new pistons/rings etc..? Hope this makes sense LOL:42:

Ya got to love a guy that digs in quickly and just goes at it.

For what it is worth, I would suggest just getting the bike running and putting a some miles on it before digging in to it too deep. The different spark plug thing would be a concern to me. Too hot or too cool a plug can make a difference in how it runs, I'd work on getting that OEM plug back in there.

Best of luck.
 

mfc392

New Member
Yeah I'm just gonna try to get her running at this point and I will worry about the other stuff down the road a ways. I need to start buying some tools!! Youtube has some pretty good videos on these bikes
 

69ST

Well-Known Member
The one nagging concern I have, at the moment, is whether or not re-tapping the plug threads deposited filings inside the engine. Wouldn't take much debris to shred the cylinder & piston skirt, possibly even seizing the rings. I am not saying that this has happened, don't have anywhere near enough info. Further, this would be a worst-case scenario...and...drum roll please...would not be fatal - to engine or wallet. One way, or another, you'll be able to make your engine healthy again. There's just a learning curve in your near future. Have to agree with Oldfishguy, you're coming across as someone motivated and talented enough to get through this successfully.

The spark plug cap only screws onto the HT lead and it's a very fragile connection. Fortunately, that really IS good enough. Usually, clipping-back about 0.250", or so, is enough to get back down to a clean, solid, end, then re-screw the cap back into place...permanently, legitimately, repaired.

As for valve lash adjustment vs compression loss, if either valve is prevented from seating fully due to insufficient rocker clearance, then yes, compression will bleed-off instantly. IF that's the problem, it's a really easy fix. Rotate the flywheel, by hand, until you feel compression then align the "T" mark, then check valve lash settings. As a quick check, as long as you can feel slight movement of the rockers, by hand, the valves are closing fully. OTOH, if there's tension on the rocker(s) that never goes away, you may have found the source of your compression loss.
 

mfc392

New Member
Sweet! I'm waiting till I have a free day to tackle these issues. Sounds like it shouldn't be too hard. Any tips on removing stripped screws and others that seem to be "stuck". Maybe WD-40 for the stuck ones to loosen them and worst case getting an extractor for the stripped ones?
 
Worst case scenario for removing the stripped Philips screws would be using a die grinder to cut a notch in the head of the screw then use a flathead screw driver with a hammer to tAP the stripped screw loose. I found this effective without damaging the engine case but obviously the screws are not reusable then.
 

Tripod

Well-Known Member
Sweet! I'm waiting till I have a free day to tackle these issues. Sounds like it shouldn't be too hard. Any tips on removing stripped screws and others that seem to be "stuck". Maybe WD-40 for the stuck ones to loosen them and worst case getting an extractor for the stripped ones?

Do yourself a favor and spray down the bolts you think will be stuck since you cant get to it for a few days.
 

Enginedoctor

Well-Known Member
MFC if you're gonna get into this, buy just what you need for tools, IMO. Start with a basic, but brand name (craftsman is a decent option here) 1/4" ratchet. 14mm, 12mm, 10mm, 9mm sockets. wrenches of the same size are probably a good idea. 12 point combination. again brand name or they'll break when you least expect it. Also, for those screws, or what's left of them, you NEED a quality impact driver (not a power tool, a thing you whack with a hammer) and a JIS 3 philips style bit. that's a must. i've spent days of my life patiently removing those screws and not stripping them. if you're desperate to remove them, you can drill directly in the center (be careful it's not wood) of the screw head, with a tiny pilot hole, then step up the bit size until the head drills off. this way you can at least remove the cover and then soak the threads with penetrating oil and deal with the rest of the screw later. thats like worst case scenario. the points are under that cover so it's a must to get to the flywheel. if you're gonna replace the points, a flywheel puller is a must also. cross that bridge when you get to it.

As for the head. just like racerx said, you might have gotten some aluminum shaving debris in your cylinder. IF that is the case, it means it might need a new one.(piston/ rings that is, +machine work) It worries me a lot that you went from a 10mm/1.0 thread to a 12mm/1.25 thread. Not only did you bump out 2mm of material, but you changed the pitch of the thread significantly. that might have been a 'no going back' deal. I doubt at that point a heli-coil would work. that would have been your best bet.

since you've already turned the motor over a bunch of times, should there have been an excess of garbage in the clyinder, the damage is already done :( Next time, if there is a next time, coat the flutes (non threaded potion) of the tap with wheel bearing grease. this way the shavings will stick in there instead of filling your cylinder.

as for the carb, i'm disappointed you went and got a new one already. your old one is japanese, your new one is (probably) chinese. something about patent stealing, cheap labor, and human rights violations that puts me in a vendetta kinda mood on those carbs. I'm being hypocritical here, having one myself, but if i were to have retained the stock size, i would have stayed with the keihin all day. It's just higher quality, and the parts are easier to source, considering you know what it is. i urge you to rebuild it, and yes you NEED a kit to make it come out right. Those carbs just 'work' with the ct70's unusual fuel delivery setup. the tank is hidden, the RES has it's own respective gas line, the petcock is on the carb, the choke is on the left side and doesn't interfere with the airbox, etc.

So at this point, you could do a compression test, or even remove the plug and look into the cylinder with a GOOD flashlight. at least the hole is bigger now so you can get a better view :21: If you see a whole bunch of filings in there, looks like you'll be pulling the top end for sure. I think you might have to pull the front wheel, or at least turn it out of the way to slide the head off of it's studs, but if you take your time and stay organized it's not too bad.

and of course, welcome to the forum. we're here to help keep these bikes alive.
 

Fuglet01

Member
Did you adjust the clutch to factory specs? If it is slipping it'll give the impression you have no compression as the engine is no being cranked over when using the kick start.
Just another thing to check.

Mike.


If it ain't broke. It soon will be!
 

mfc392

New Member
So after I got out class today went with my buddy to Harbor Freight and picked up a drill, screw extractor, some more wrenches, a wire cutter and some misc. items. Spent about $50... Extracted screws off flywheel cover, I adjusted the valves and trimmed the wire like you guys said to do and she's got spark and compression. Took the carb back off it and I think I'm gonna try adjusting the float etc... so I'll let ya guys know how it goes!! Appreciate all the advice and tips BIG TIME. Next big task might be electrical... Prob have some bulbs burned out.

- Mitch
 
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