questions about CB 350

ditrone · Posted: Thu Jun 26, 2008 12:22 pm Post subject: questions about CB 350

Hello new to this forum. I just picked up a 72 cb350 twin and it leaks oil of course from the seals, oil comes out of where the points are as well, around the two wires. i got a seal kit and i'm gonna do what i can there but something that bothers me is it spits smoke out of tube coming from the top of the engine routing done to the bottom of the bike. constantly. Any ideal whats going on here? Bike runs, kinda loud ticking sound and in neutral it revs through the ranges fine but when riding it doesn't like going above 5k rpm, 55 mph. Is the motor shot on this bike? sounds like a sewing machine! Also one pipe gets hotter quicker then the other. The carbs have been rebuilt and he put straight pipes on it so it's loud as hell.
Bike has oil in it. The vin on the frame is not the same as on the bike so does that mean it's not the original motor? thanks for any help

jayel · Posted: Thu Jun 26, 2008 8:46 pm Post subject:

smoking out the crankcase vent is rings or valve guides,check the compression that would also be why it doesn't want to rev, cold cylinder low or no compression or dirty carb

Johnny5 · Posted: Fri Jun 27, 2008 6:26 am Post subject:

The Vin number and frame number will be different.

These bikes naturally have a lot of engine noise and vibration, but oil coming from the top vent hose could also mean too much oil?

As far as oil coming out where the points are, that's just a little gasket that needs replacing. Hit up Autozone for gasket material and cut your own for real cheap.

About the reving, that could be dirty carbs, especially with one side running hotter than the other. You should check your petcock for good fuel flow, then clean tank if it's rusty, then off with the carbs and begin cleaning them out. Then start with a fresh tuneup.

Like Jayel said, check the compression.

Hope this helps.

ditrone · Posted: Fri Jun 27, 2008 8:18 am Post subject:

Very helpful
thanks

LilLance · Posted: Mon Jun 30, 2008 9:20 am Post subject: oil coming out the pcv vent

Yeah I've got knida the same problem with my 70 cb350. The oil starts coming out the pcv/vent tube out the top of the engine when im doing anything over 60mph. I don't know what could be causing it. I've check'd damn near everything w/o taking the engine completely apart. I've tuned the carbs to running/idle near perfect, burning right. Im not burning any oil whatsoever. The case isn't over filled. The oil filter is clean. It has good even compression in both cylinders. It goes thru all the gears no problem. It has no problem accellerating. Both cylinders are at a pretty even temperture when running. There is efficent fuel flow. Cleaned the petcock, the carbs, made sure there's no vacuum leaks. Everything runs in tip top shape, except for the oil that comes out the top of the engine outta the pcv valve when im doing 60mph or over. I have no idea what could be causing the engine case to pressurized so much to cause 2quarts of 10w40 to be pumped out!?
Does anyone have a suggestion, or idea of some sort of tsb maybe about this issue?

Johnny5 · Posted: Mon Jun 30, 2008 9:37 am Post subject:

Dont know if this would help, but have you cleaned your oil filter?

LilLance · Posted: Mon Jun 30, 2008 9:48 am Post subject: cb350

Johnny5 · Posted: Mon Jun 30, 2008 7:15 pm Post subject:

I would say to check the rings, but you say it has good compression. Hmmm...maybe do a leakdown test and make sure the rings are good.

ditrone · Posted: Sat Jul 12, 2008 2:21 pm Post subject:

Ok thanks for all the help folks, unfortunately i don't have a compression tester. I need one badly. Today while messing with this bike i noticed that it seemed to be much louder on one side of the engine (left). I finger revd the carbs on each side and on one it revs well (left) but on the other it just sucks air and doesn't rev the engine (right). I also noticed it has condensation building up on that side(on the right carb) and it was cold! also a little oil coming out of the exhaust pipe on that side. also unfortunatly the stock pipes are gone and it has pod filters. The bike will rev up into the rpm ranges fine but while riding it, just doesn't want to go above 4 and a half thousand rpms.
So to get to my point, should i pull and check the carbs? I don't think they are configured to stock specifications either.... It leaks gas as well, out of the overflows, both sides.

ditrone · Posted: Sat Jul 12, 2008 2:28 pm Post subject:

wanted to note the carb (right side) got cold and wet when i pulled the pod filter off while it was running. That might of been why it did that.

ditrone · Posted: Sat Jul 12, 2008 2:36 pm Post subject:

also wanted to note i don't think it was running this poorly before. I mean it was running like crap and weak but now the exhaust (stupid str8 pipes) just seems overall quieter. still just as weak though.

ditrone · Posted: Sat Jul 12, 2008 3:09 pm Post subject:

going to buy a compression tester, if i wanna keep messing with motorcycles i'm gonna need one.

ditrone · Posted: Sat Jul 12, 2008 6:30 pm Post subject:

ok i got 130 on the side running good and 160 on the side that won't rev correctly.
cold
meant to mention this bike only has 4k original miles on it supposedly.

Johnny5 · Posted: Sat Jul 12, 2008 7:00 pm Post subject:

Hmm, usually the side that has the least amount of compression is the one that should run more poorly. Maybe you have a carb problem.

A real quick check to see if you have decent compression: Pull the spark plugs and put your thumb on the plug hole. While holding your thumb down with some pressure, have a helper kick the bike over. The pressure from the cylinders should pop your thumb off the hole. If it does, you have decent compression and can start looking at other things.

With your gauge readings, 30 off from one side is a sign something is going wrong inside the motor.

ditrone · Posted: Sat Jul 12, 2008 7:33 pm Post subject:

when i check the compression with my tester do i need to remove both plugs?
I was leaving the one in while i checked the other, throttle full open and choke open as well.
key off