Yup,the Spares Drawing is wrong! Larger diameter is innermost. A sleeve on a standard bolt is a poor solution, the sleeve will only distort. Helicoil 5/16" BSF and make the thread the full depth, just short of hitting the steering column. It is best to use the standard 5/16 BSF hexagon on the bolt, as otherwise you might foul front forks on full lock.You can drill the heads after noting fully tight position and fit a lockwire (black plastic sheated for unobtrusiveness) across the front of the UFM.The right sized washer 3/8"x7/8" is likewise essential. Also, check the other end of the tank and the distance piece for your source of vibration-and everywhere else on the machine!
Tank bolts shaking loose
- Thread starter danno
- Start date
I just refurbished a UFM that had been drilled and tapped out to 3/8 UNC and very poorly at that. Took it out further to 7/16 20 and made inner and outer "threadserts". Outer 7/16 20 tpi and inner is 5/16 -22 bsf. Ran them in with studlocker locktite and gave them a slight peen at the joint. seem to work well, but won't be on the road for a real test for a few months yet.
Hi Howard.No the rubbers are in the correct way.Here is my take on it all:
I found that when tightening the bolts (at first, when rubbers too tight) the smaller diameter of the rubbers i.e. the outermost bit, compresses, swells and grips the tank bracket, then as the bolt is tighened further the brackets are pulled inwards with the rubber,until the bolt nips up against the shoulder.This bends the whole tank inwards slightly, stressing the whole deal up.The spacer tube at the REAR of the tank would not go between the tabs when the front mounts were tightened, but when i loosened the front mounts, it slipped in easily.The thing with Vinny tanks is that the central section, over the top of the oil tank is so "shallow" in relation to the rest of the structure that they flex and bend like a book opening with surprisingly(alarmingly?) little effort. This discovery made me spend the time setting up the front mount assembly so that there is only the very slightest compression on the rubbers when the bolts are nipped up against the shoulder- the tank is held nicely without any stress (which of course is the whole idea) it cannot move about due to the opposing shoulders on the rubbers and everything is stress free with the bolts securely nipped up on their shoulders. With little or no compression on the rubber, the rubber does not exert any twisting or loosening torque on the bolts because it is not squashed onto them. Ideally,the tank brackets,(are they straight?) fitted with the rubbers the correct way with the larger dia inside, should pass over the bosses in the head stock as a snug sliding fit with no sideways play- if there is i would suspect the tank/brackets to be distorted outwards and correction necessary. It may be that some of the rubbers supplied are more "generous" than they once were, or the washers thicker, bolts shorter or even wear on the counterbore in the headstock,- any or all of these things results in squashed rubbers preventing the bolts from tightening properly, and makes people struggle trying to compress rubbers pushing on the bolts to start the thread- which is were the threads start to get crossed up and stripped ! Set the whole deal up with the absolute minimum of compression on the rubbers, and the bolts will go in with fingers, no struggling, tank will be sitting in stress free repose and bolts will tighten correctly onto their shoulders and be secure I`ll wager, regards, Bob.
I found that when tightening the bolts (at first, when rubbers too tight) the smaller diameter of the rubbers i.e. the outermost bit, compresses, swells and grips the tank bracket, then as the bolt is tighened further the brackets are pulled inwards with the rubber,until the bolt nips up against the shoulder.This bends the whole tank inwards slightly, stressing the whole deal up.The spacer tube at the REAR of the tank would not go between the tabs when the front mounts were tightened, but when i loosened the front mounts, it slipped in easily.The thing with Vinny tanks is that the central section, over the top of the oil tank is so "shallow" in relation to the rest of the structure that they flex and bend like a book opening with surprisingly(alarmingly?) little effort. This discovery made me spend the time setting up the front mount assembly so that there is only the very slightest compression on the rubbers when the bolts are nipped up against the shoulder- the tank is held nicely without any stress (which of course is the whole idea) it cannot move about due to the opposing shoulders on the rubbers and everything is stress free with the bolts securely nipped up on their shoulders. With little or no compression on the rubber, the rubber does not exert any twisting or loosening torque on the bolts because it is not squashed onto them. Ideally,the tank brackets,(are they straight?) fitted with the rubbers the correct way with the larger dia inside, should pass over the bosses in the head stock as a snug sliding fit with no sideways play- if there is i would suspect the tank/brackets to be distorted outwards and correction necessary. It may be that some of the rubbers supplied are more "generous" than they once were, or the washers thicker, bolts shorter or even wear on the counterbore in the headstock,- any or all of these things results in squashed rubbers preventing the bolts from tightening properly, and makes people struggle trying to compress rubbers pushing on the bolts to start the thread- which is were the threads start to get crossed up and stripped ! Set the whole deal up with the absolute minimum of compression on the rubbers, and the bolts will go in with fingers, no struggling, tank will be sitting in stress free repose and bolts will tighten correctly onto their shoulders and be secure I`ll wager, regards, Bob.
Hi Bob, I'll read that again when my brain's more awake. I think I see what you're saying, I'll have a look at the proper Vins at the club run tomorrow, fortunately I just used to slide the tank on my Comet and put the bolts in.
Morning Chankly, I didn't say the tube was the right way to do the job, just a quick fix. Not all owners have engineering skills, or access to machining facilities, and it's the start of the riding season (in the UK). I've always worked in engineering, and I've still had to wait 3 weeks (up to now) for a machine shop to respline a kickstart for me.
H
Morning Chankly, I didn't say the tube was the right way to do the job, just a quick fix. Not all owners have engineering skills, or access to machining facilities, and it's the start of the riding season (in the UK). I've always worked in engineering, and I've still had to wait 3 weeks (up to now) for a machine shop to respline a kickstart for me.
H
I wrap tape around the oil filler neck to keep from chipping the paint around the hole in the tank. Also, I put layers of tape squares on the nuts on the upper Girdraulic link studs that hang over the tank.
Thanks.
I can see how the threads become stripped.
I need to have a careful look to see how much the rubbers are being compressed before the bolt shoulder
tightens up or indeed if they are in the correct way.
Would like idealy to sort it out without re-tapping.
ive said this before .
make sure the rubbers under the rear of the tank are thick enough not to allow the distance peice foul on the rear valve cover as you tighten the two bolts up.
this could crack the weld at the rear end, don,t ask how i know.
OSSIE
make sure the rubbers under the rear of the tank are thick enough not to allow the distance peice foul on the rear valve cover as you tighten the two bolts up.
this could crack the weld at the rear end, don,t ask how i know.
OSSIE
Conversly Ossie, make sure that the rubbers under the rear are not so thick that the rear tank distance piece hits the stop valve assembly, causing it to vibrate and crack out of the UFM. Things are quite tight in this area and constant checking for the clearance of things is essential.
Bruce, I have a short lenght, 3" to 5", of push bike tube in my special tools box that I use to stretch over the neck of the oil tank so that the paint remains unscathed during fitting and refitting. Tuck the loose top of this down into neck to stop anything falling into the tank whilst the cap is off.
Bruce, I have a short lenght, 3" to 5", of push bike tube in my special tools box that I use to stretch over the neck of the oil tank so that the paint remains unscathed during fitting and refitting. Tuck the loose top of this down into neck to stop anything falling into the tank whilst the cap is off.