Peder_y2k

You said: 1. Is there any way to tell if the oil is synthetic or not? Answer: Heat a teaspoon sample to 800°F for 10 minutes. If the sample turns to ash, it is mineral base dino oil. If the sample turns to a highly corrosive acid, it is synthetic. -Pete, in Tacoma WA USA

there is not enough money in ALL of North America to get me to eat at a Burger King!!!! That's exactly my thought about McDonalds................. I go out of my way to eat elsewhere, such as Burger King and Wendy's etc. McDonalds burgers just taste like dirt -Pete, in Tacoma WA USA

'88VR..........took the diaphragm covers off for some checking, and found dampness in the area circled in the attached pic. 3 out of 4 carbs have this wet spot. What would account for this? -Pete, in Tacoma WA USA

Yes, tabs removed. -Pete

Only thing I can think of is if the hole is in the 'shadow' of the needle. There could be a very slight difference if one is in 'shadow' and the others are not. That's just a guess on my part. -Pete, in Tacoma WA USA

I'll be darned...... the relocated TCI box (TABS REMOVED) to top of the air filter box rubs the underside of the cover on my '88VR. Didn't do that on my previous '83. What to do to prevent contact rubbing............. other than relocate it inside the left fairing with the radio system? -Pete, in Tacoma WA USA

This will be my last and final comment on engine braking. While engine braking isn't "harmful" to the engine, it will cause additional wear and tear on the engine. During engine braking, engine vacuum becomes very high. This causes more oil to be drawn past the rings and through the valve guides . This additional oil flow can lift accumulated piston carbon that can scratch the cylinder walls. The rings are designed to seat under pressure, a vacuum causes them to lift off the walls causing a different contact patch resulting in more rapid wear. The load on the piston (reverse of the load when firing) becomes high. This isn't harmful in the general sense, as this occurs to a degree when simply letting off the throttle. However, under high rpm, the forces in the motor are in a different direction and higher then usual. Also, the piston is more likely to slap the cylinder walls . This is not to say don't use engine braking. I do it with full knowledge of the circumstances. However, an engine used for braking will wear (or wear out) faster than one not used for braking. Engine braking is used in motorcycle racing, but engine life past the end of the race is not as important to the racer as winning. Brake pads are cheaper to replace than rings and valve guides. Heavy engine breaking is more detrimental to engines, clutches, transmissions, and drivelines than light engine braking, and I recommend using a combination of both regular brakes and engine braking where practical and done with due consideration. -Pete, in Tacoma WA USA

It is possible that the wash water has collected somewhere critical and is shorting out some of the ignition componants producing an irregular spark. Another day drying will reveal if that is/was the issue. -Pete, in Tacoma WA USA

"perhaps you can expound on the damage done to an engine when engine braking?" Very simple - a motorcycle engine was designed to produce motive power, not the reverse. The engine, transmission, and drives under compression speed control are stressed (both mechanical and thermal) at different pressure/contact points that were never designed for the purpose of braking. Big trucks are quite different, they are usually diesel, expected to negotiate long descents with loads etc. and were designed for such use. Motorcycles were not. Treat your motorcycle like a truck and it will wear out/break. The owners manuals make no mention of using engine compression for speed control on long descents, and that's because it isn't recommended. If they built motorcycle like trucks, they'd all be way over 1000lbs. and relatively lethargic. Never use engine compression for heavy sustained speed control on mountain grades like Pikes Peak. Only use it if you have no alternative........or you have lots of money for repairs. I know the design of my '88VR and both the intermediate and final drive do not lend themselves well to constant reverse pressures that are present with engine braking. -Pete, in Tacoma WA USA

Engine rebuild is more spendy than brakes. Note that I suggested several cool-off stops on descent. Could also help cool with spray bottle, and at those temps the water turns to vapor so fast that warping a rotor is negligible. Much easier and cheaper to fix worn out brakes than fix a worn out engine/tranny It's your machine, but don't ask to use mine on that mountain. -Pete, in Tacoma WA USA

No problem going up. Walking around at the top will exhaust you fast (less oxygen for activity), so plan accordingly. Comming down is an issue for brakes as they get smokin' hot and loose stopping ability. It is far cheaper to wear out the brakes than to use engine compression to maintain speed. I suggest you stop several times on the way down for at least 15 minutes per stop for brake cooling. There will be a hot brake inspector 1/2 way down that uses an infrared non-contact thermometer on your brakes, and will tell you if you are a go or no-go for the continued descent. Been there and done that several times. -Pete, in Tacoma WA USA

OK..I accept the concept that a vacuum imbalance differential between carbs can be an issue of improper fuel mix, but then the return springs MUST be exact matches, and that is highly unlikely. A few millinewtons (1oz. = 278 millinewtons) difference in spring pressures would make for an imbalance between carbs. A perfectly balanced set of return springs would be very costly due to selective tolerances, but the springs are relatively cheap. I suspect spring pressure differences are actually in the many tens of millinewtons making balanced carbs impossible. Still open and receptive to input. Inquiring minds want to know........... -Pete, in Tacoma WA USA

OK.......... If the system is so sensitive (presuming that it is very sensitive) to vacuum, then there ought to be serious driveability issues with altitude change, but there aren't. It is a known fact that 3000ft. elevation change from sea level will make a 10% reduction of vacuum............that's significant, yet the bikes can tolerate 10,000 ft mountain passes easily enough with only a slight loss of power due to less oxygen. I'm suggesting the system is not that sensitive to be affected by a few pinholes in the diaphragms So, please convince me otherwise..........or am I missing something here. -Pete, in Tacoma WA USA

So I post a question about a throttle response issue, and the concept of pinholes in the carb diaphragms come up...again....as in numerous articles posted on this forum. I just don't get it. Someone enlighten me, please. BTW, I have a degree in mech engineering, so I'm not ignorant. The factory manual clearly states on examining the diaphragm for issues, to look for rips and tears, No mention of holes or pinholes at all. So in examining the piston valve (slide), there is a large designed in hole in the piston itself that passes vacuum through to the other side of the diaphragm. Duh? So what difference do a few pinholes make? Should be negligible. The built in hole is so large as to be some 20-30 times the size of a pinhole or 3. The engineers at Yamaha would mention 'holes', or 'pinholes' in the diaphragm if it were an issue, but they don't. I can understand the rips and tears as these can easily be much larger than the built in hole, but the pinholes concept seems vacuous at best. I'm wondering if the pinholes concept isn't someone's invention. Attached is an image of the manual section describing the diaphragm inspection, and a diagram of the piston (slide) with the hole designated with a red line. -Pete, in Tacoma WA USA

Don't just get ANY small charger, it MUST be a "smart charger" . An ordinary small charger will cook the battery dead because it won't stop charging while plugged in. A smart charger is designed to be left connected and will measure the battery voltage and turn itself on and off to preserve the battery -Pete, in Tacoma WA USA

Tweeks found her own place to park away from the cars and other bikes and we didnt even bother hauling out our traveling motel,, or tent if you prefer.. Just another nights rest for a couple of tired bikers and one tired ol bike.. Puc Oh come on Puc......that's a staged pic and you know it. A seasoned biker like you and Tip would sleep on the soft grass in the background in front of the motel for some real shut eye. -Pete, in Tacoma WA USA

Looks more like it went to that toggle switch on the left in the pic. If there's nothing for the toggle switch to operate, take that wire lead off the battery post. -Pete, in Tacoma WA USA

Uhhhhh................efficiency? -Pete, in Tacoma WA USA

Tool only works when shim is missing, but would certainly function for cam lobe pushing the bucket down against the pressure of the valve spring. A spacer like a 25¢ piece placed under the tool could move the bucket down even more -Pete, in Tacoma WA USA

Went thru the pressure sensor system 1000 miles ago, but will check it again for leaks and go thru the test process again. - thanks -Pete, in Tacoma WA USA

Probably related to that aftermarket toggle switch seen in the image. -Pete, in Tacoma WA USA

I'll check the diaphragms. Last time I had the carbs apart, the diaphragms were OK. Thanks -Pete, in Tacoma WA USA

1988 VR - runs great, well tuned/maintenanced, no problems.............yet. I don't usually ride fast, but yesterday (hot day for here -90°F) on a group ride with some church-types through the moutains, found myself at a sustained 80mph. on the interstate. When I opened the throttle for more speed to catch the prayer group, the engine would not respond to the increased throttle demand and happily stayed at 80. I know these bikes are fully capable of two-up riding at 120mph all day long. Beginning to think the fuel pump is not keeping up. Anyone know the fuel delivery rate? Note: 1000 miles ago, I'd cleaned the carbs and fuel tank replaced the fuel filter, and replaced the pump to carbs fuel line with 5mm urethane hose. Maybe the hose is too small, but it matches the pump and carbs fitting diameters. EDITED NOTE: On hard acceleration up to 7000RPM shifting thru the gears, there were no issues. Issue occurred only at sustained high speed -Pete, in Tacoma WA USA

The old Ford requires only 39psi fuel pressure. I'm going to make a close examination of the pressure regulator. -Pete, in Tacoma WA USA

I found myself holding my breath there for a moment Ed. -Pete, in Tacoma WA USA