I have an old Honda 650 four, and I'm planning on using the engine on an off road buggy project. The engine runs, but has carb issues. Since I don't have a really strong background in bikes, I started to wonder if there might be a simpler way to provide fuel to this engine. It wouldn't be hard to fab up an intake manifold to mount a single carb, but would it work and would it make any sense to do?
Just thinking on this one and looking for input. While it would be cool, I'm not interested in fuel injection.
single carb has been done but it a major pain in the ass trying to get equal mix to all cyl. Their was a twin carb set up made for a while but best bet is to fix what you got or go with another set of carbs.
You could stuff on a set of Lectrons as thier easy to set up and once set you never need to mess with them but there not real good on off throttle control and most don't have a choke so cold starting is a pain.
Are the stock carbs pretty good if rebuilt?
sould be just fine it cleaned well. Do your self a big favor and keep the M/C air box and use it on your project. Everyone thinks pod filters are the way to go...only if you own stock in a jet company.
44Dwarf wrote:
sould be just fine it cleaned well. Do your self a big favor and keep the M/C air box and use it on your project. Everyone thinks pod filters are the way to go...only if you own stock in a jet company.
Thanks. Can you go into a little more detail on that last comment about filters and jets? I'll have to look, but I don't recall if I got the air box with the bike or not.
The first thing most people did in the old days was take a hacket to there bikes and smash the E36 M3 out of the air box then stuff pod filters on them. Pod filters completely change the jetting requirements. If the carbs are of the CV type (don't know your year) then you end up with a real mess to try and jet as the filters can cut the air side to the diaphams and can mess with the laminar flow thu the carbs inlet that the air box and conector hose smooth out.
What year honda are we looking at here?
I believe it's a '76. So if you re-jet it, can you make them work, or are constantly messing up because of the filters?
Bikes from that era were real sensitive to jetting. As 44Dwarf mentioned, people would put on K&N filters, usually with a header, and then they'd fight the jetting until they got tired of the bike and sold it. If you can, keep the stock airbox and exhaust, it will save you a lot of messing around.
The carburetors are probably gummed up if the bike has been sitting for a while. Take them apart and clean them, or bring them to a bike shop to have it done.
In reply to stuart in mn:
Do the carbs have fuel pumps in them or is the fuel supplied by gravity feed? I only had the engine running once. It actually ran fairly well, but I had to hold a gas can up high above the bike with a fuel line to the carbs to keep it running.
Sorry, I'm sure I could tell if I spent a little time with them, but it's been a while since I've even looked a this project, and I'm at work right now.
Most are gravity fed, but I've had some where a vacuum is required. Pull the fuel line off the tank and nothing happens, no vacuum.
YMMV.
The stock setup was gravity fed, high volume low pressure. Most fuel pumps will overload that setup. So I'd look into the vacuum operated fuel pumps used on lawnmowers etc, they are cheap and two should fit your requirement.
I'd say stick with the stock carbs too, jetting replacements can be a PITA. Take advantage of the money Honda spent on engineering the stock setup.
More questions for you.
You say its a 650cc 4 cyl? sure its not a 550 or a 750?
It should be stamped on the side of the cyl block nromaly right above the HONDA on the side cover but on the cyl.
Double check the year cause no 650 in 70's untill 79 and that was a CB650 if that is it then you have some nice mecanical operated round slide carbs (non CV type) that should provide more then enought proformance.
Yes they were orginaly gravity feed if you plan on having the fuel cell / gas tank lower then the motor you will need a pump like Airtex E8016Sthat supplys 2.5-4psi at 12 volts. You'll also need a regulator the dial type suck with the new feul and will not work well go with the holley type http://www.jegs.com/i/Holley/510/12-804/10002/-1
Ran that airtex pump in my dwarf for years with dial type reg but soon as alky hit the pump both were lost with in a year. Replaced the pump with same unit and the reg with the holley and sold that car and next one went Injected.
I know for sure it's a 650. I'm not sure about the year, so maybe it's a '79. The tank will be mounted above the engine. So will gravity feed be adequate?
I think the 650 may have come out in 1978, but no earlier than that. There weren't a lot of them and I'm pretty sure they were all "Custom"s, meaning early touring/cruiser style.
I've owned a bunch of four carb Honda's and have to echo what everyone else said. Nothing messes up a nice Honda engine faster than pod filters. They sure look cool, though. Stick with a stock airbox and be happy.
Don't try to outsmart Honda engineers.
It's too bad I didn't know about this project last fall; I gave away a CBR 600 engine with carbs for a case of beer.
Carbs are easy to clean. Worst thing to happen is a torn diaphram.
For sure stick with the stock setup. Make sure your petcock and all the lines are open and that fuel runs freely when you pull the hose off the carb. Go through the carbs thoroughly after a good soak in carb cleaner and make sure every last air bleed and passageway is clear. Set the float level. Also make sure the inside of the tank is clean and free of rust and other junk. I must have been through the carbs on my '76 KZ three or four times. I'm hoping this last time is the LAST since I thoroughly cleaned the tank and painted it. So far this year, the bike's been running great, knock on wood.
