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Honda VF750F - 1983-89 {{forumTopicSubject}}
Hey MG
jeg har næsten fået mig foræret en Honda VF750F som jeg vil ud og hente her i weekenden. Den skal sættes i stand og mangler lidt stumper hist og her. Og så kan den ikke starte, det vides endnu ikke hvorfor da den har stået stillet i en 5-6 år
Er det en kværn der er værd at gemme på? Går de godt sådan nogen?
Jeg kan se at de kan komme til at blive rimelig rå at se på hvis man fjerner frontkåben/lygten og sætter en Custom lygte på
jul 2006
Følger: 10 Følgere: 26 MC-er: 3 Emner: 56 Svar: 1.397
jul 2006
Følger: 10 Følgere: 26 MC-er: 3 Emner: 56 Svar: 1.397
feb 2011
Følger: 1 MC-er: 1 Emner: 11 Svar: 74
Ja den sorte du havde var da flot.
Jeg har dog aldrig kørt med V-motor, men det er nok et spørgsmål om tilvænning
jun 2008
Følger: 4 Følgere: 3 MC-er: 1 Emner: 58 Svar: 3.189
Engine Issues
The Interceptor had one endemic engine issue in the V4, the camshaft. In 1984, camshaft wear issues started to arise and people started to complain. At first Honda did not admit that there was a problem. After conducting further research, they discovered that the camshaft wear was most likely caused by oil flow issues. Honda issued a recall on the bikes and added kink free oil lines and less restrictive Banjo bolts. They also made adjustments to the engine heads by drilling holes in the cam lobes and capping off the hollow cam's ends. This did not fix the problem, so Honda went back to the drawing board. The first thought was that the issue was heat related, but after further investigation the real problem was discovered. There was too much clearance in the camshaft bearings. Honda fixed this by changing all the camshafts with new components. This fixed the camshaft issues but wounded the reputation of the V4.
In the 1980’s one bike single-handedly destroyed Honda’s reputation for reliability. Take a bow the legendary VF750F. Honda’s sports-tourer was fraught with top-end problems. The surface of the cam was too soft and regularly pitted, causing the cam to wear unevenly and wobble in the bearings. As well as making the engine rattle like hell this destroyed cam chains and cam chain tensioners, leading to engine rebuilds. This bike coined the phrase ‘chocolate cams’ and made it commonplace in any owner’s vocabulary. To silence critics Honda brought out the legendary VFR in 1986 which was a big loss leader. Honda took a hit to restore their battered reputation for reliability and completely over-engineered the VFR to make it absolutely bullet-proof. Which it still is to this day.
Read more: http://www.visordown.com/motorcycle-top-10s/the-10-biggest-biking-blunders/15731-9.html#ixzz2TUitKohN
Well first of all, the VF750 Sabre or V45 Magna, I think, came first, and are different engines. One or both of them are shaft drive, and the cylinder inclination is different.
They are 90Degree V-fours, but pretty sure that the V is more reclined.
On the VF the V is more inclined with teh front pots almost parallell to the floor, rear ones almost verticle.
Maga / sabre have the pots tlited back more.
Internally they are quite different too.
I have a VF1000F of '84 vintage, and it has Magna / Sabre cousins too, and NONE of the internals are interchangeable from research I've done....
so that's that one.
as for the cam-shaft ledgend.....
Here goes!
As far as I can gather OFFICIALLY the first batch of VF750 cams were not properly hardened.
with a bit of guess work, I THINK they were cut on blankd for the sabre engine... (Sabre had been in production for twelve months prior to 'Inteceptor' launch) But the Sabre was much more softly tuned and didn't have the same lift or duration as the Interceptor cams.... so when cut to a wilder profile, more metal was taken off them, and that cut through the surface hardening... but thats only speculation!
According to HONDA it was all fixed in the US (who recieved ALL the first production run) under warranty or by recall.
But there was also an oil feed issue. There are two spray bars over the cams. They are braxed up, and it seems that the pipe work was a tad on teh small side, and revved hard, if the spray bars weren't 'matched' to teh galleries, could starve oil to the cams.
There were three or four successive mod-packs, I believe in the Honda service book for this, which included a different oil filter, drilling out some oil galleries, and I THINK replacing the early cam spray-bars completely.
In Europe, they claimed that the 'original' problem had been cured before any bikes got to these shores, but some of the mod-packs were supposed to be checked or done by dealers......
There is a LOT of 'lore' surrounding teh whole issue, and it SEEMS that the reputation was a little exagerated.
In the US there were afetr-market oiler kits that added an extra oil cooler and external plumbing to give the cams a better supply.
But they got the bike for three model years and got a LOT more bikes than we did.
Big bikes were NOT selling well in the UK at that time, and the press scare over the VF750 didn't help its sales figures at all!
I had up until not long ago, a 1985 copy of Motorcycle & Motorcycle Mechanics with a picture of a silver suited 'robotic dancer' on the front next to a VF750 with the slogan 'Only for Robots', and an article inside asking whether a quad-cam 16valve watercooled engine was just ONE step too far..... and whether the typical motorcyclist, could EVER get to grips with DIY mechanics on something so heniousely complex...... remember, the Triumph Bonnaville was still listed as a 'new' bike back then, and plenty of people bought them becouse they knew they could take them apart and put them back together again....... A Suzuki GSX550 with double over head cams was 'scary' mechanics, for the more experienced DIYer!
Possibly explains quite a bit about the legend.... it WAS a complicated engine...... still is!
But it was just legues away from what people of the time were used to, and rumours of having premature failures was something VERY scary!
People ridiculed Honda Cam-Chains, and the reputation for old hondas to start knocking at 24K either throught cam chain stretch or the tensioner blades giving up, was something that made people steer clear of buying them second hand, as they expected hefty repair bill, or a DIY nightmare to fix them..... an engine that could eat its own head and had twice the number of cam-chains AND a water-jacket round everything was ESPECIALLY scary......
But the MAIN problem was that for all teh engine technology, they weren't a very spectacular bike!
95bhp and I cant remember the quoted weight, think it was about 425lb..... it was under-powered and over weight against the competition.
Bench-mark for it was the Kawasaki GPz750 'unitrack', which was only about 5bhp down on power, and something like 30lb lighter. Had a reputation for being 'unburstable' in the engine room, and a sweet handling bike.... AND cheaper..... why would ANY-ONE want the VF750F, and all the pottential problems it had?
Honda BASICALLY admitted they had completely cocked it up, becouse within months they launched the CBX750F, which had almost the same 95bhp as the VF, without the weight, and went head to head withthe GPz, and fared well.
But the air-cooled four's days were numbered, water cooling was essential if power was to increase much more, so Honda had to percevier, and they were locked into the V4 concept, as market fears were that a water-cooled in-line four would be even wider than an air-cooled four. At the time, a GPz750 could be written off, just falling off its side stand, becouse if the genny cover broke, impacting the flywheel could bend the crank!
ANYWAY....
The here and now is...... is its survived thirty five or more years, without eating its head...... its probably been sorted!
If you still have concerns, I believe that NEW heads are actually still available..... certainly were for the less common VF1000 not long ago.... AND surprisingly NOT that expensive! Think they were only something like £125 each....... mind you DO have to buy two of them!
AND theres the US aftermarket exernal oiler kit.... which I just CANT remember the name of!
So, as a 'classic', it is an interesting one to go for, with a LOT of history to its credit.
As to the Rothmans bikes..... I seem to recall some consternation over those!
Pretty sure Ron Haslam was mixed up in it, & they got a Yank team manager from US Superbike, who had some rather curiouse ideas about the UK Superbike regulations......
Basically, under US regs, ALL they had to use of the stick road bike was the frame and engine cases! In the Easter-Cup series, the ?Yanks were just leaving the brits for dead on the straights, as they had such much more highly tuned motors!
Anyway, this chap from teh states looked at the regs, and decided that the 'key' was in the wording, which said something like 'standard parts' had to be retained, but may be 'modified'..... so set about cutting crank-shafts in half and welding them back together, and melting down original pistons and re-casting them..... which is where I think the ACU decided he had crossed the line!
Think he did pretty much the same thing with the early VFR, which was more awkward to tune due to teh cassette cam-drive, which meant if you skimmed the head to increase thc ompression ratio, you retarded the cams, and due to back-lash ideler in teh cassette, there was oly so much you could take off the head or deck-height.
His mods eventually resulted in the VFR750R 'homolugation special' or RC30 as its more commonly known....
But thats another leap!
Bottom line?!
There were numerouse flaws in teh VF750 motor, from the notoriouse Honda cam-chain tensioner mechanisms, to teh oil feeds to teh cams, to teh cams themselves.
The engine was overly ambitiouse in conception, and rushed into production to stay ahead of the original GPZ600 & 900, and paid the price.
BUT its reputation was also exagerated by a LOT of scare mongering, in an era where its complexity was just a HUGE leap of the imagination.
So, today?
If you find one, and it runs..... no more or no less likely to self destruct than any other thirty five year old bike.
Far more will depend on how well its been looked after.
If you want one as a classic, though, well, its got a lot of classic cudos by way of all that history going for it......
And today? Well its not THAT much more complicated than we've become accustomed to.
ONLY think to note with them is that they have 'thin-wall' pressure die cast cases....... suposed to make them light! (Thats a laugh!)
But becouse the metal section is so thin, when dissassembled you need to handle them carefully as they can crack easily, and on assembly you HAVE to be critical with the low rate torque wrench to make sure that all the cases are pulled up evenly and aren't sistorted by tightening.
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mar 2013
Følger: 25 Følgere: 18 MC-er: 3 Emner: 23 Svar: 1.332
Det tog tid for olien at smøre tilstrækkelig i topstykkerne ved koldstart. Og under 3000 o/min. gav systemet utilstrækkelig olietryk, noget som blev værre på ekstra varme dage
læs her
http://www.janekneis.dk/honda-v4.dk/v4teknik_2.php
der finder man også en løsning på det problem og bemærk at dette ikke er gældende for vfr'en
jul 2006
Følger: 10 Følgere: 26 MC-er: 3 Emner: 56 Svar: 1.397
aug 2011
Følger: 17 Følgere: 24 MC-er: 5 Emner: 53 Svar: 1.489
dec 2003
Følger: 2 Følgere: 84 MC-er: 10 Emner: 240 Svar: 20.505
okt 2007
Følger: 4 Følgere: 5 Emner: 18 Svar: 489
okt 2007
Følger: 4 Følgere: 5 Emner: 18 Svar: 489
Jeg stod i lære da VF750 blev lanceret, og jeg husker stadig det specialværktøj importøren udsendte sammen med cyklerne. Værktøjet er en form for indstillelig 'krog' som løfter knasten op mod overfaldet. Dette skulle monteres ved måling af ventil tollerance, da knasten pga. dens korte længde 'vipper' i lejerne når den skal åbne den modsatte ventil. Benyttede man ikke dette værktøj, gav det forkert udlæsning af ventilspillerummet.
dec 2003
Følger: 2 Følgere: 84 MC-er: 10 Emner: 240 Svar: 20.505
Samme "specialværkstøj" skal også bruges på min VT250. Jeg bestilte det fra nyt i UK til 150-200kr. Så værre er det altså ikke.
feb 2011
Følger: 1 MC-er: 1 Emner: 11 Svar: 74
Honda VF750F - 1983-89