tore down the honda passport last nite

merlin311 /

i called three friends we had it down to the frame in no time only thing that took time was labeling parts.im buying piston rings and a gasket kit today.

Re: tore down the honda passport last nite

Cool! Is this the one that had no compression? If so, did you find the culprit?

Smart idea to label everything especially when you have 6 hands taking parts off!

Got any pics?

I always find it's good to take pics in case someone wants to see how to do a certain job on their similar moped.

Oh boy

Who said it "had no compression" ??

I read what he said at first... and he said "it had nothing" ... which only means it didn't pop or fire (when coming from a rookie).

How much compression do you think a 70cc 4 stroke has?

they are not hard to kick thru at all.

it probably had a dirty carb and didn't need to be disassembled at all.

(if more info was given later I admit not reading it)

Those 4 stroke Hondas are pretty tough... they can go for 30 years on one top end under average useage.

Hope they get it back together OK.

Re: Oh boy

Ron Brown /

Fred,

Your "sometimers" is happening again. : )

The subject of his original post was "No Compression".

You have to admit, I tried my hardest to talk him out of disassembly until he found the problem.

I'm with you, I never met a Jap 4 stroke that needed rings, unless it was re-bore time or the rings were really corroded.

Ron

Re: Oh boy

Ron and Fred

I read his post and I am having the same symptoms with the c70 I just bought. It had been sitting for 2 years. I bought a manual, because I am new to 4 strokes and it said esssently the same thing you had stated. The manual said the cause could be;

defective head gasket

bad rings

stuck valve

burnt or poorly seated valve.

It said put about a teaspoon of oil in the cylinder, put the plug back in and try it again. It said if the compression got better in was probably rings. It said if it didn't get better probably bad head gasket or stuck valve. Mine did get a little better but not much.

I am going to check the valves to see if I have one that could be rusted and sticking. I want to make sure it is a not a stuck valve before I crank it too much and bend it if it is a stuck valve.

The odometer shows 10,000 which isn't much for one of these engines.

I am going to clean the carb as SOP and I checked the reticifier and it was OK and I am getting a new battery (this is a 1981,6 volt system)

The is the Evil Kanevil bike I bought in San Francisco.

I don't know how much resistance to expect with this C70 but I have 3 Honda Urbans Expresses, 2 strokes, that are kick starts and they have quite a bit more resistance when I kick them. They usually start first or second kick. Love those Urbans but they only top out at 30 mph. I am looking forward to getting this C70 going as it is a 70 cc and is supposed to get around 50 mph top end.

I am proceding according the manual

Re: tore down the honda passport last nite

Where are you getting your parts?

Thanks

Re: Oh boy

Ron Brown /

Zippy,

If you were going to bend a valve, you allready have. Try a quick compression test with a guage. That will eliminate all the confusion.

Ron

Re: Oh boy

The manual says to start it and let it warm up and then do compression test and it should be 170 psi warm, but since I can't start it do you have any idea what the compression would be cold?

Re: Oh boy

Ron

Here is what I thought I would try.

I'm going to crank the engine to TDC and then put in my compression fitting without the gauge and then shoot about 160 lbs psi in through the compression fitting. If I get air out the exhaust I figure I got a stuck or poorly seated exhaust valve, if it comes out the airbox or carb, it's an intake valve problem and if it blows out the oil filler hole I have a ring problem.

I figure this is easier than tearing into the engine and if I have to I'll know what I'm looking for.

Does this make sense?

Re: Oh boy

Ron Brown /

Good question! I don't really know, but I cant immagine it would be a lot less. Just make sure you have the throttle wide open and try a swift kick and a a slower kick. If you have leaky rings or valves, there should be a big difference between slow and fast because you allow more time for leakage.

Ron

Re: Oh boy

Ron Brown /

Zippy,

Sounds good to me, however, I would not worry so much if the rings are blowing as they could be stuck in the grooves and may free up if you run it and heat cycle them a few times. If it is a valve, look at the stem through the exhaust or inlet port and see if it is gumm that you can clean off without disassembly. Even if it is rust, if it is only a little of the stem and you can scrale it off, you still have plenty of good guide surface left.

Ron

With spelling corrected

Ron Brown /

Zippy,

Sounds good to me, however, I would not worry so much if the rings are blowing as they could be stuck in the grooves and may free up if you run it and heat cycle them a few times. If it is a valve, look at the stem through the exhaust or inlet port and see if it is gum that you can clean off without disassembly. Even if it is rust, if it is only a little of the stem and you can scrape it off, you still have plenty of good guide surface left.

Ron

Re: tore down the honda passport last nite

merlin311 /

well hmm im not really a newb to small four stroke hondas.and i got to torn down the gaskets are shot and so are rings while im at it im also having the head rebuilt.the carb looks good. mine has 12k miles on it.Zippy wrote:

>

> Where are you getting your parts?

>

> Thanks

Is either valve off its seat or not ?

Since you have the head off.. are either of the 2 valves being held off the seat once the camshaft is out ?? (stuck)

If not... then you might not need to do anything to the head.

Hold your mouth securely over each port (intake and exhaust)... and see if you can pressurize it with your lungs and feel a leak.

If it leaks... you could just lap the valves (or tell the mechanic to just lap them).

if you have an honest mechanic... thats what he should/would do.

Re: Is either valve off its seat or not ?

Ron gave me the same good advice about looking through the ports at the stems to see if they are visibly rusted or gummed up. Mine were!

The easy but not very accurate way to check compression is to simply put your thumb over the hole and crank her over. If the air doesn't seep by your thumb then is seeping by a stuck valve. That's how I checked mine initially.

When you get the valves out of the head look closely at the stems because if they were stuck open then they are most likely bent ...even bent slightly means they must be replaced. Check the piston top also for breakage where the valve would have hit it.

Expect to pay about $25 for the intake and $31 for the exhaust valves. I've been getting all my honda parts from www.troy-racing.com They're pretty good.

good luck!!!!

Re: Is either valve off its seat or not ?

OK thanks Don

Re: Is either valve off its seat or not ?

merlin311 /

the exhaust valve is stuck.i think all im going to have them do is order

new piston rings

full gasket set

and redo the head.

he said 150 to completly rebuild the whole topend but.

i can assemble it myself plus the help of a sixty year old man that gave me the moped.hes been working on them since he was 14.hes also got a honer.now all i need is a hot tank-.-

im goin out to start taking afew more parts off then comes the fun thing of sanding the camo paintjob off it.then this week it will be going over to its original yellow color.Zippy wrote:

>

> OK thanks Don

check the paint job on this one

Here is nice a 1983 Sapphire Blue one

Honda_C70_1983_SAPPHIRE_BLUE_1.jpg

Re: tore down the honda passport last nite

merlin311 /

yea mines missing the plastic peices up front.i think im going to paint it a nice semi gloss black.since its not being built to be the prettiest and i have cops that love to give us hard times with our mopeds.so im not painting it a bright color

it'll make those rides after 10pm easier when theres supposed to be no minors out.

alright laters all im goin to bed.

happy superbowl everyone.. going to my dads friends for a party tommarrow:)

Re: Is either valve off its seat or not ?

merlin311 /

when the cops came by three times tonite again i decided against yellow.

Update to Ron Brown on Honda C70

Ron I missed the part about having the throttle wide open when i did the conpression test on my C70.

I found little gal out here in the Bay area who is an AMI certified motorcycle mechanic that will come to your house and do repairs. She put the compression tester on the Honda C70 and kicked it a few time and said, there is nothing wrong with your compression (about 120 cold) should be about 170 warm. I ask her what i was doing wrong and why my test only showed 50-75 lbs. She said you have to have the throttle open all the way when you kick it. Then I reraed your post, missed that part.

We also tested and I have good spark. we used starter fluid and the bike tried to fire up so basically i just have to drain the old gas, clean the carb and fire it up.

She only charged me $30 to come to my house and do this. Motorcycle mechanics out here charge $95 per hr and you have to take it to the shop and beg them to work on it, although they are starting to see a slow down with all the Dot Comers out of work.

So I feel good that I don't have to tear into the engine and the moral of the story is to read what people write or listen to what they say.

I have a theory that if mankind would only listen to voices of experience we would be advanced a 1000 years beyond where we are today and be exploring the stars now. But alas most of us have to learn the hard way by trial and error and not by the voice of experience.

So anyway thanks Ron and next time I will read your posts more carefully.

Hope you are having fun in Austin and picking up a lot of Aggie jokes

Zippy

Re: Update to Ron Brown on Honda C70

Ron Brown /

Zippy,

Don't sweat it, most of us miss the obvious when we are reading something we think we understand already.

I hope your mechanic looked as good as she worked. : )

Ron

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