Hey all! i have a vf750f that i picked up 4 very little. There is a slap sound on idle from the engine, and the diaphragms are all torn. I fixed them marginally and the bike ran like a rocket for 2 weeks till they tore again. The bike starts 1st time every morning - love hondas! anyway - i am thinking of replacing (in order of priority) diaphragms/ cam chains (+ tensioners??)/rings/valve seals. I know the old saying is - if you open the engine, replace everything. Is this worth it? maybe ill ge away by just slipping through new cam chains through the heads for now (the linked ones) - leave the rest as is? bike uses hardly any oil and compresison seems great - minimally i would then only need new top gasket (can u reuse it?) and the chains instead of the whole lot? dont scratch if it aint itchin, right? I look fwd to hearing the mixed responses - i am personally veering toward the minimal fix - and spend $$ on front wheels / rear shock rebuild / etc. I also want to remove the top cowel and have a naked look - meaning i would need different clocks. Perhaps newer honda firestorm or something?
Howdy, i just rebuilt my husky single cyl 450 from the ground up. blew the main bearing. it is true they will try to charge you through the roof!!! They wanted $3500 for the parts and labor... i sourced them the parts and gave them just the motor and saved just over $1000. i know you don'twish to go this far as your motor still runs and may only need minor work, and i recomend you dont get too carried away as hondas are bulletproof, but i heard mine run today for the first time since the rebuild and am very very impressed!!!
slap the cash on the new cam chain and tensioners, new carby manifolds, like rockitman187 said check your valve clearences. new plugs and new filters all round and you will be laughing your way around every corner
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I would think that the screws have limiter caps, so you cannot turn them all the way in.
1) put both screws at the maximum you can turn them out
2) start and warm up the engine
3) at idle speed, turn the L needle in till the engine speeds up (by itself) and then starts to lower rpms.
4) from that point, turn the L needle back out till engine raises and then lowers. Leave the screw in a setting that the engine sounds a little rough
5) use the same procedure with the H screw (at full throttle)
6) now throttle up from idle
does the engine pick up quickly? settings are good
does the engine stumble and then finally begin to pick up?
Then turn the H out about 1/4 turn. If needed for rough but smooth running, turn the H out again another 1/4 turn.
*Please Note: 2cycle engines should ALWAYS sound just a little rough at full rpms. NEVER adjust a carburetor so that the engine 'screams', you will not have an engine for very long at that condition.
The knocking sound that you hear may be coming from lifters, crank bearings or piston slap. How old is the oil change, is there enough oil inside the engine, and is it due? How many miles are on this engine? All of these suggestions are normal with higher mileage vehicles. The only one that doesn't involve rebuilding the motor is the lifters. A lot of times replacing the hydraulic cams will fix lifter noise. I hope this is what you were looking for please write back. If you have any questions, let me know, good luck.
sounds like a bad rod bearing. if auto trans put in drive hold brake firmly with left foot gently push on gas pedal with right foot if knocking increases with engine rpms bad rod bearing time for engine rebuild
With the black smoke, it sounds like it's running rich (too much gas going into the motor). Remove a spark plug and take a look at it- if it's all black and sooty, then yes, your motor's running too rich and you need to lean out the fuel mixture. I'm not positive, but that truck probably has a carburetor and you could do the adjustment yourself, with a little help from a shop manual. If it's fuel injected, you'll want to take it to a shop or a friend that knows what they're doing to get it adjusted right again.
If the spark plug has little tiny clumps of stuff stuck to it you're burning oil, and that's a bigger problem. An oil leak means a fairly major engine rebuild is in store for you. If it is burning oil, I'd just drive it like it is until it eventually conks out or something else goes wrong on it. Unless, of course, the truck is special to you and worth investing in an engine rebuild...
It may be piston slap. This is caused by either engine wear with the piston bores being too large for the pistons, or by poor manufacturing tolerances, or a combination of both.
To test for this, start the engine up first thing in the morning and run it for about thirty seconds while you listen carefully and memorise the sound and
intensity. Turn the engine off quickly, remove the spark plugs and put two
squirts of motor oil into each cylinder. Reinstall the plugs, start the
engine up again and listen. If you have piston slap the noise will have been greatly reduced or even
eliminated for about thirty seconds seconds and then returns.
The fix is to rebuild or replace the engine, but if it works just fine then don't worry. Many slappy engines keep going for tens of thousands more mile. The fact that your knocking is only at idle suggests your crankshaft is not to blame.
Your oil is thinning out too much. Lucas oil additive would be a great thing for this or an oil change with a little heavier weight oil The other cause of this could be piston slap from low grade fuels.
There is enough residual oil left on the cams to take care of the first 20 rounds of rotation. The cam damage doesn't occur at start-up, it occurs while lugging at low rpms in a high gear, i.e. when the engine is under heavy load at low speed.
The problem has nothing to do with the "oilpipes" or their thickness. The problem is two-fold. There was a large batch of soft cams that wore prematurely, and the bikes made from '82 to at least '86 had oil supplied to the cams and rockers from a low-pressure, unfiltered source. When warmed up, the cams have about 4 psi at idle and it never gets over about 25. With a simple modification, the idle pressure goes up to about 12 psi and tops out at over 50
I did my oil modification in about a half day with normal shop tools. If I can do it, anybody can.