Question about 1988 Honda CBR 400
I have a honda 400 nc23 1998 model for some reason when running only the left hand 2 downpipes are getting hot the right-hand side ones are stone cold the spark plugs have a very strong spark the carbs are immaculate and I have lots of compressions I also replaced the fuel pump and put an inline fuel filter on it, but still only 2 of the downpipes are getting hot please help me. @
Hi, Tj20262 you need "FIVE" things in order for a cylinder to run properly:
1. FUEL: in order to validate your not getting fuel spray some starting fluid into the air cleaner and hit the starter button, if it fires up and runs for a few seconds then you know you have a fuel delivery issue. Multi carb banks should be bench "SYNC"
2. SPARK: remove the spark plug and with it connected to the spark plug cable ground the threads to something metal you should see a bluish white spark if not you have a faulty spark plug, spark plug cable, ignition coil, condenser, CKP, ECM, sensor or the wiring in between.
3. COMPRESSION: you must have at least 80-100 PSI for most bikes, multi-cylinder engines should be within 10-15% of each other if not perform a leak down test you may have a burnt or bent valve or hole in the piston or broken rings.
4. CAM TIMING: confirm your timing marks are aligned to see if the cam chain or adjuster are worn out and the chain has skipped a couple teeth.
5. IGNITION TIMING: on older bikes check to see if your points have not closed up, timing plate has not become loose and confirm with a timing light for proper retard and advance functions, on newer bikes where timing is controlled by an ECM and is nonadjustable check you CKP, TPS, MAP, O2, sensor or its counterpart for integrity.
For more information about your issue and valuable "FREE" downloads that you will need for viewing or printing please click on the blue links below. Good luck and have a wonderful day.
two dead cylinders please help CBR Forum Enthusiast forums for Honda CBR...
Honda Cbr400rr 1988 1999 Service Repair Manual
Posted on Feb 02, 2018
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Posted on Jan 02, 2017
SOURCE: honda pal 2 stroke scooter
Are you adding oil to the gas? (32/1 = 4 ounces per gallon)
Do you still have spark? Install a new stock spark plug.
Clean the carb, but follow these steps >
Remove the carburetor from the engine.
Remove the float bowl and clean the entire carb with a spray carb cleaner from the auto parts store. Wear protective goggles to avoid getting spray in your eyes. Spray into all the little airways and fittings in the carb. Remove the two screws on the outside throat of the carb and spray into the screw holes as well.
< < READ CLOSELY > >
Be sure to put these two screws back in the same hole they came out of. IMPORTANT > do not tighten these two screws down. Only screw these in until they LIGHTLY seat. Now turn each screw one and one half turns outward. Put the rest of the carb back together, clean the air filter and install the carb. Let the float bowl fill then start the engine. Let the bike warm up then set the idle speed. This process should get you back on the road.
Posted on Mar 31, 2009
hi i had the same problem try checking your fuel pump there are contacts on the bottom of it under the black plastic if they look burned out then its the fuel pump if not try the fuel pump relay its located next to the pump on the side of the battery box bridge the black and black/blue wires to bypass it hope this helps
Posted on Apr 29, 2009
SOURCE: cbr250rr 1990 model won't start
Guess I should post my answer as a solution so you can rate the solution. Clarifications can't be rated. Any results yet?
The timing should be okay. Sitting for two years will not change it. Pull all the plugs and give a shot of WD40 into each cylinder while pushing the starter button. This will get some lubrication to the cylinder walls and piston rings. It will also help the rings to seal up. Now do the compression check. The readings should be within 10 psi of the top reading. If using aerostart, spray it into the air cleaner not the carbs. The air cleaner will greatly lessen the chances of a fire caused by an engine backfire. Always have a fire extinguisher on hand when messing with the carbs.
Bear in mind that some of the rings may be stuck in the piston grooves and will not be free to spring outward to seal against the cylinder wall. The WD40 may help here also. The worst case is that you will need to pull the head and cylinder to physically free the rings. Your pike is now 19 years old and the valves have probably never been worked on. Now would be the time to re-seat the valves. Depending on the condition of the cylinder, piston and rings, you may want to re-bore the cylinder and mount new piston and rings. At least run a cylinder hone through each cylinder.
I was going to just post this as a "clarification" but have sort of gotten into it now. All I ask is a "Helpfull" rating The "Thanks for trying" rating is a real bummer for a guy just trying to help. Get back to me.
Not sure what manual you have but compression is never checked at anything above idle. Crank and idle speed compression should be 140 to 160 psi.
Posted on Jun 03, 2009
SOURCE: Fuel from engine breather pipe
There are just three ways for fuel to get into the top end. As mentioned, bad valve guides (exhaust guides are just as old as the intake guides). Bad rings with raw fuel getting past the rings. Either way, fuel is getting up there. Time for a valve job and fresh bore with new pistons and rings. If able to find the parts, I would also install new cam chain and tensioner. You have a very early CB450. Today's VIN numbers have 17 numbers. That is what didn't seem right.
Go to the site below where you can see a parts diagram for your specific bike. I already checked and a lot of parts are available for your bike. You will select the actual brand, year, model, etc., once you go to the site. Part numbers and prices are also shown. You can order parts from this site. In the event no price is shown on a particular part, the part is not in stock. www.babbittsonline.com/pages/parts/viewbybrandand/parts.aspx
You can also Google 'vintage motorcycle parts honda" and find stuff there.
Top rating for this answer? Thanks!
Posted on Jun 10, 2009
When I recently ordered parts from Saber Cycle, they included a piece of information that pertained to my motorcycle, which is also a 1983 Honda Goldwing GL1100 Interstate. Here is what it says, I hope this helps:
Air Cut-Off Valve
The air cut-off valve is an extremely important part of the fuel/air intake system that is frequently missed even my competent mechanics, most of whom are not even aware of its existence or how it functions.
Every GL1000 has one, located in the air intake tube, between the air cleaner box and the manifold. Every GL1100 has four, located in the top air intake passage of each carburetor, and every GL1200 has one located in the plenum box below the air cleaner box similar to the GL1000.
These valves are "air blockers", along with the carburetor o-rings, serving to restrict air flow and increase the fuel/air mixture ratio when the carb slides are in the lower RPM range, up to closed so that the machine will start and idle smoothly with virtually no choking and accelerate rapidly, with no stumble or hesitation.
When typical starting requires heavy and prolonged choking to keep the bike running, when stalling and hesitation occurs even while "warmed up" and when backfiring pops while the throttle is shut off while cruising, most people will start fooling with the air screws to try to overcome the problem, only making it worse along with reducing their gas mileage.
Running with dysfunctional air cut-off valves can causes severe engine damage or failure. When the valves are dysfunctional, the engine pulls nearly total air in the low RPM range through the carbs and on to the combustion chamber. The fuel/air ratio is extremely poor with pre-ignition long before the normal 38 to 40 degree firing point, generating an enormous amount of heat, with no power, which is trapped a longer period of time in the cylinder before the exhaust valve opens.
This heat goes mostly up through the cylinder head, gradually incinerating the head gaskets and allowing engine coolant (anti-freeze) to seep into the engine. You can easily spot when you are in trouble by a puff of bluish-white or white smoke on first starting the engine. Don't leave it alone. Change head gaskets immediately or you could take out your bottom end bearings, ruining the engine.
For those of you installing new exhaust systems, you will discolor your headpipes, either blue (lean state) or gold (rich state). You can destain your pipes using "blueaway" or "blue-off" but be careful not to rub the chrome, just dab gently.k These compounds are usually purchased at a Harley dealer or Harley oriented aftermarket shop.
Honda genuine pipes, like many Yamaha pipes, have a double wall for a portion of the headpipe which masks this discoloration-but also masks a bad state of tune. Even if your pipes are original and still in good shape, don't think that you are OK if the bike has any or all of the dysfunctional air cut-off valve running and performance characteristics.
If your 1975 to 1987 Gold Wing is not getting 50-58 miles per gallon (20-23 KM/Liter), you have one of the most obvious signs of trouble. It is likely your air screws have been backed out to try overcome the effects of the poor running, stumbling, starting and stalling and quitting.
Resynchronize all four carbs to the #3 carb vacuum level using mercury carb sticks or vacuum dial gauges. Stay with strict use of the setting levels in either the Honda, Clymer or Haynes manuals. Do not attempt to tune any other way! Guessing will not work and can cause considerable engine damage!!!
Posted on Sep 26, 2009
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