Tuesday, July 26, 2011

RE: [Honda-C70] Re: Top Speed Issue

Charles : Your post that you can almost pull a wheelie going to second gear with the engine reved , popped a red flag for me . My 81 does that when the back tire is lower that recommended . Owners manual calls for 28 psi front & 40 psi rear with cold tires. If your tire manufacture has a max recommended pressure try closer to max than 40 minimum. Maybe that will get 2 or 3 more MPH for you. Try 1 thing at a time & test so you don`t get into the "something worked but which thing was it" problem. Also my 81 runs fastest in spring & fall temps of 50/55 degrees . I missed all that last year when it would not start. Good Luck ! Baby Huey

To: Honda-C70@yahoogroups.com
From: mgladu@mindspring.com
Date: Tue, 26 Jul 2011 10:40:50 -0500
Subject: Re: [Honda-C70] Re: Top Speed Issue


At 6:02 AM -0700 7/26/11, Charles Schlosshan wrote:
>A, Thanks for your suggestions and I will try and answer them.
>- Tire pressure is 35psi
>- Oil is 10W-40 motorcycle oil and the oil pump is operating.
>- Brakes and chain are correct. Chain and sprokets are new. Gas is
>fresh this week.
>- Carb is new and jets have been checked and cleaned. Air filter
>has been blown out and looks fine. A new filter should be here
>this week.
>- Tuning has been done over and over. Ignition timing is advanced a
>little just because the bike runs better that way. Carb is perfect,
>no bogging at all.
>- Cam timing is on the marks.
>- Smooth level road, there are a few here, is where I can get
>35-37mph. I usually set upright as do most scooter riders here. I
>come from the sport bike crowd so lying down on the bike is
>possible. CBR1000RR. One member suggested setting the point gap at
>the upper end of the adjustment span (.018mm) and give the condenser
>more time to recharge. I did this, was .012mm, and gained the
>additional 2mph I didn't get before.
>- Throttle cable has a little more play then 5mm; visual inspection
>shows the slide completely opening the carb throat. I will adjust
>it when my parts arrive.
>- Clutch is new and does not slip. The bike will almost do a
>wheelie when shifting to 2nd gear with the revs up.
>- Since the previous owner apparently never changed the oil I don't
>think it has had any slippery crap in it.
>
>I and running out of things to check/replace/repair so any
>suggestion would be appreciated. I tried to check the muffler for
>flow just using my hand. Hardley anything comes out the end at idle
>and not much more rev'ed up a little. The muffler was rusted anyway
>so I ordered a new one from Beatrice Cycle along with a new cylinder
>head. I think one of my valves may have been leaking a little. I
>could detect a little puff sound around the head that I would have
>called a burnt valve if it was a car. Anyway that is the last item
>I can replace on the upper end. The engine feels like it is trying
>to rev on up in third gear, sorta like a surge for a second or so.
>(?) I would think that would be the ignition timing but I have
>moved it everywhere possible to move it. A little advanced is where
>it runs the best. With the timing set on the F mark it runs really
>sluggish. Any Comments?

I would:

Put the ignition timing back 'on the marks' to have a better idea of baseline.

Change to a new condenser and points (if you haven't already).

Do a compression test (looking for better than 125psi).

Set the float level higher (as high as it will go without overflowing
on the sidestand).

Go to 40psi (can't hurt).

Make sure the chain has some free play (too tight will cause drag).

Spin the wheels off the ground to be sure the bearings aren't trashed.

There are a few pages in the online manual that take you through
every obvious and not so obvious step of troubleshooting slowness.

Check them out.

http://autos.groups.yahoo.com/group/Honda-C70/files/C70%2080-81%20Passport%20Shop%20Manual%20%28JPEG%29/172.jpg

http://autos.groups.yahoo.com/group/Honda-C70/files/C70%2080-81%20Passport%20Shop%20Manual%20%28JPEG%29/173.jpg

http://autos.groups.yahoo.com/group/Honda-C70/files/C70%2080-81%20Passport%20Shop%20Manual%20%28JPEG%29/174.jpg

Mike G.
-

[Non-text portions of this message have been removed]

------------------------------------

C70 Passport Not Running Right?
1970-73 C70 Honda Service Manual: http://tinyurl.com/6ebwtw
1970-73
C70 Troubleshooting Guide:
http://tinyurl.com/6ebwtw (scroll to sec.7.1 page 101.jpg)
1980-83 C70 Honda Service Manual: http://tinyurl.com/hu42c
1980-81
C70 Troubleshooting Guide:
http://tinyurl.com/hu42c (scroll to sec.18-1 page 170.jpg)
1982-83 C70 Troubleshooting Guide:
http://tinyurl.com/hu42c (scroll to sec. 20-28 page 205.jpg)

1980-81 C70 Maintenance Schedule: http://tinyurl.com/z4zn6
1982-83
C70 Maintenance Schedule: http://tinyurl.com/hw35c

More resources for C70 Passports and Cubs:
http://www.shlaes.com/Vehicles/Scooter.htm
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