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Sounds more like a rod knock......possibly. Hard to tell over computer audio. Here is a quick and dirty way to tell. Remove one spark plug (leave one in for compression resistance) and manually rotate the engine while looking down one plug hole. Stop rotating as the piston is on its downward stroke. Take a screwdriver and push down on the piston lightly. If the piston moves before trying to rotate the crank, you have a bad rod bearing. There should be no perceivable slop between the piston, rod and crank.

Repeat on the other cylinder
 

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It might be worth balancing/cleaning your carbs before going any further.
 

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Discussion Starter #23
Sounds more like a rod knock......possibly. Hard to tell over computer audio. Here is a quick and dirty way to tell. Remove one spark plug (leave one in for compression resistance) and manually rotate the engine while looking down one plug hole. Stop rotating as the piston is on its downward stroke. Take a screwdriver and push down on the piston lightly. If the piston moves before trying to rotate the crank, you have a bad rod bearing. There should be no perceivable slop between the piston, rod and crank.

Repeat on the other cylinder
Thanks for the tip 8ball! I'll see what happens.

Just checked out your Suzuki build thread, awesome stuff!
 

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Discussion Starter #24
It might be worth balancing/cleaning your carbs before going any further.
Good call, others have said the same. I started out by (like an idiot) tearing into the front forks and brakes. I wanted to replace the seals in the forks (they had some weird looking corrosion going on, turned out to be water from the cracked dust seal), and because I'm a novice I figured I would just rip out the whole triple tree and headlight. Anyways, It needed new brake pads and the calipers were a little scratched up. Long story short Ive cleaned the all the brake components and the pistons all look to be in real good condition. The rotors are in good shape, but I'm still kicking around the idea of new drilled and slotted ones for better braking in the wet of Berlin. I cannot for the life of me find any that bolt up to this bike. I checked EBC and SPS and they don't have any, unless I fucked up the search. I'm going to paint and seal them, then put the front forks back on.

At that point I can clean the carbs and start er up again.
 

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Discussion Starter #26

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It sounds disgusting.... always hard to diagnose via recording. If you are going to crank the engine over (with starter) with a plug removed, or run it on one cylinder to see if its one cylinder or the other making the noise... don't just let the unused plug lead hang there. Probably best to short it out to ground. If you are just turning it back and forth with a wrench, it doesn't matter. Doesn't sound like piston slap and that would be relatively rare in one of those engines. If something is going to go south due to lack of oil, the cam bearing surfaces in the head are first to go, so "usually" you'll get the death rattle in the upper end first. As suggested, set up the carbs, but before you do..... Adjust the valve clearances, cam chain, and don't forget to adjust the balancer chain. If the balancer chain adjustment has been ignored for a while. that could be a source of at least part of that expensive sounding racket. I would sort that out before you spend money on exhaust etc.
 

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Discussion Starter #28
If something is going to go south due to lack of oil, the cam bearing surfaces in the head are first to go, so "usually" you'll get the death rattle in the upper end first. As suggested, set up the carbs, but before you do..... Adjust the valve clearances, cam chain, and don't forget to adjust the balancer chain. If the balancer chain adjustment has been ignored for a while. that could be a source of at least part of that expensive sounding racket. I would sort that out before you spend money on exhaust etc.
Boom! Thanks for the tips, seriously. I’ve got a set of feeler gauges coming in next week with a micrometer, so I’ll get it going. Time to tune!!!
 

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Have you mentioned what you have done so far engine-wise?
Any bike i buy used, i will try to drop the oil pan and check for debris and clean out oil pick up screen.
Check air filter, change oil filter and check the plugs. Check the fuel filter and carb overflow lines. Drain the carb bowl and look at the color and smell of the fuel coming out. Check the plugs and wires. Look at the coils for any major cracks.
Check the carb boots, crankcase valve and line to airbox.

Address what you find then start in on tuning. Tuning is wasted on an engine not in good working condition.
 

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Discussion Starter #30
Have you mentioned what you have done so far engine-wise?
Any bike i buy used, i will try to drop the oil pan and check for debris and clean out oil pick up screen.
Check air filter, change oil filter and check the plugs. Check the fuel filter and carb overflow lines. Drain the carb bowl and look at the color and smell of the fuel coming out. Check the plugs and wires. Look at the coils for any major cracks.
Check the carb boots, crankcase valve and line to airbox.

Address what you find then start in on tuning. Tuning is wasted on an engine not in good working condition.
Awesome stuff. I’ll do all that once i can start it again.

I havent touched the motor. I pulled The air filter foam which was old but not damaged... other than that I haven’t touched it.
 

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:I thought it Almost sounds like it's running on one cylinder,

did you do a compression test? If there is anything wrong with pistons rings or valves that will give you a pretty good indication.

oil pressure test? If the oil pressure drops below spec, start looking for worn oil bearings.
 

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Are both exhaust headers getting hot?
 

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Discussion Starter #33
I've been reading through this forum over the weekend, and damn if some guys aren't missing out on killer information. Seems like people egos are getting in their way on this forum in many threads. Thanks to all of you who have chimed in here, you've saved me a ton of time and money already. The advice is appreciated, thanks boys!

So, now that my approach has beens set straight here... The new plan for the bike looks like this:

1. Finish the forks and put the whole triple tree back together with the wiring harness.
2. Run through the list of engine maintenance items firstly------ address any issues.
3. Run through the list of engine tuning items secondly---------- address any issues.

Here is a list of the items that have piled up for items 2 and 3 in the last few days in this thread;

Engine Maintenance Items (in no particular order)
o Drain oil, inspect for metal shavings
o New Oil
o New Oil Filter
o Clean oil pickup screen
o New Air Filter
o New Spark plugs
o Inspect spark plug wires
o Check Fuel Filter
o Check carb overflow lines
o Check coils for major cracks
o Check carb boots for wear
o Inspect crankcase valve
o Inspect line to the airbox
o Remove carb bowl, inspect (smell, look, scratch around)
o Check front brake pads, shoes, rotors (done)
o Check rear brake drum for leaks
o Inspect drum pads for wear
o Inspect chain and sprockets (likely going to replace anyways)

Engine Tuning Items (in no particular order)
o Check Valve Clearances
o Adjust Cam Chain
o Adjust Balancer Chain
o Check for compression
o Check for Rod Bearing wear
o Possibly Remove and sort out the Carburetors
o Check oil pressure

Put it all back together and then start it up. Go from there, having covered the basics first.


At this point, fire it up and see if the disgusting sound is gone. Go from there....

In the mean time, I will buy a new chain and sprockets. I think I am going to get a rear sprocket with an added tooth, since I'll be driving this thing in Berlin traffic exclusively. Thoughts? The idea is to improve off-the line acceleration at stop lights.


Thanks again for your help guys.
 

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Sounds like you have a sensible plan. If your chain and sprockets are usable just leave them until you have had a chance to ride the bike, running properly, in stock configuration. You need to know where you are before you can decide what direction to go.
 

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Oil pressure is easier to test on some engines then on others depending on the pump location and the path the pressurized oil follows, some chains have no facility to adjust tension, pretty sure the balancer chain would be one of those, get good at cleaning carburetors, modern fuel has shelf life similar to milk, all of the carburetor fuel born pollutants will be in the bottom half of the carb, the top half will rarely need attention unless rubber parts start to rot. It's the little brass parts in the lower half of the carbs that need regular attention, they are the jets and little tiny orifices that get plugged up with dirt, if you see green colour stuff in the float bowl that is copper that has leached out of the brass parts. One tooth change on rear sprocket will make very little difference, one tooth change on the front will make a noticeable difference because the ratio change will be more significant. Most street bikes have what is called a 'wide ratio' transmission, generally this means 1st and 2nd will be geared low and close to each other, higher gears have a wider ratio change between them, top gear will be close to 4th on a 5 speed or 5th on a 6 speed transmission. The wide ratio gearing is designed to accommodate mixed city and highway riding, 'close ratio' gearing is typical on go fast race bikes. Changing the final drive gear ratio will need some experimentation to see if it actually improves things or just makes you shift gears more.

Go easy with pressure washers, they have a habit of driving water past oil and dust seals very easy, they work fine on tires and under the fenders but that's about it.
 

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There's no problem with using a power washer. If your focusing 2000+ psi onto the face of the seals it might, but to cut the grease and dirt off engines and frames they work great. I run a couple thousand miles a year on my ATV and power wash the shit out of it, 3700psi unit. I've never seen any indication of water penetration, that's not to say it can't happen, but it's very unlikely.
 

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i believe the main issue with brakes in the rain is the water on the discs boiling into steam and that holding the pads off the discs. one simple mod i'd try is to cut a lot of shallow grooves into the pads with say a hacksaw blade to give a reduction in pressure area and escape to see if it helps.
 

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Discussion Starter #39
Are both exhaust headers getting hot?
Both get hot, checked the spark plugs today as well and they are both good, not gummed up. They are new, but look good. Put a light into the cylinder and couldn’t see much, pistons look dirty but it’s hard to tell what’s going on in there. Listened closer and the death rattle, it’s loudest from the top end, seems to be louder on the right side. This week I’ll check off my list of to dos and see where we’re at after that
 

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Discussion Starter #40
So I’ve been digging and found the following info for the CB400t.

Front tire conversion - 100/90 x 19
Rear tire conversion- 110/90 x 18

I’m thinking the Dunlop StreetSmart. I’ll be in just less than 200 Euro for a set. Holding the weather, good lifespan, and fit the wheel.
 
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