This is more of a general question as opposed to a specific Triumph question. But, I found a used 2002 Bonneville for sale. Has 22,000 miles and looks to be in good overall condition with just normal wear and tear. Besides the obvious things such as inspecting the frame, inside the gas tank for rust/crud, giving the whole bike a once over, etc., how can you tell if an engine is worn out or not? It starts up fine, rides and accelerates fine, no smoke, no obvious issues. But the owner doesn't have any maintenance records. It's on the 3rd owner. He has his oil change record (which is basically 1). So, is there anyway to tell if the engine is worn out? Will a compression test be the only way to test the engine besides tearing it apart?
One of the best indicators is a leakdown test.
Run the engine until warm, shut it off, attach leakdown tester, position test cylinder at tdc on compression stroke.
The leakdown percentage can be read, the manual for your specific tester will indicate good, bad and ugly numbers.
Air hissing in the carbs intake indicates leakage past the intake valves, air hissing in the exhaust indicates exhaust valve leakage. Air hissing from crankcase dipstick hole or breather indicates cylinder blow by past rings.
I have a high pressure set and a low pressure set. I prefer the high pressure set. Newly rebuilt but broken in engines show 96-98 % on the high pressure tester, test done at 75 PSI.
You will need to put the bike in 5 th gear and lock the wheel, either by wedging the rear brake pedal down on or some other method. Some jam a stout stick thru the spokes and let it shove up against the swingarm to prevent piston movement when the air pressure is introduced.
I have seen weak clutches slip on adding the air pressure. This is pretty obvious as the leakdown percentage quickly goes skyhigh and lots of air is gushing thru the valves.
you have to be at or near tdc of the compression stroke (piston moving up so rings seal in bottom of ring grove.
on these bikes you have to pull the alt cover and hold the crank shaft bolt with a breaker bar and allen head socket rear wheel wont work on these you don't have enough control over the motor turn on these bikes.
22,000 is insignificant mileage on these bikes if cared for properly. A quick compression test will let you know the condition of the piston rings and valves.
If the bike is not yet yours I doubt the present owner will allow you to do a leakdown test. Are you going to turn up at his doorstep armed with a compressor, a load of hoses, plug adapters and gauges...?
I just did one for the purchaser of a bike I have for sale, it's quick to do so I can't imagine the objection from someone wanting to sell an older machine. Would depend on the seller I guess.
I have a compression tester as well, but don't use it anymore as the leakdown gives a lot more info and I believe more accurate info.
You don't need exact tdc, just both valves shut, but Mike is correct that it should be coming up on compression. It's easy enough to control by rotating the rear wheel, bike in gear. It's also good to check further down the bore as often there is more wear down in the bore.
I've tested many bikes this way, it's not a problem, don't know why a Triumph 790 would be special.
there just hard to control the motor turn by the rear wheel play in drive gears and so on valves move 2 at same time cam timing close on ex valve lots of reasons. Its only a small window of the stroke you will get it to work right on these bikes .
I been a mechanic since 1975 and these motors still teach me things.
The method I mentioned works well for the bikes I have here (including the Daytona) and any others I've tested. Maybe one day I'll test a 790 and something weird will happen.
The leakdown is a good thing to do and record in a log book along with mileage. That way you have a base number to start from.
When a bike isn't running right, or if a lot of miles have been covered, a leakdown and comparison to the base number will quickly let you know if there is a problem with rings or valves, or if things are normal and the problem is elsewhere.
If you do buy a 2002 Bonnie my only concern is the idler boss.
I would definitely buy and fit a TTP idler boss reinforcing plate.
The starter idler gear boss is a potential problem on the earlier engines.
The reinforcing plate is a pretty cheap price for the peace of mind.
All good advice. But some of it is beyond my experience. Perhaps I'll check with my dealer to see how much they will charge to do the testing and then see if the seller will allow the bike to be tested.
Why worry about it if the bike rides great, pulls hard when you give it to it and it looks great, at 22k on the clock is only just run in, I be more concern at looking over the frame to check for any repairs or signs it has be down or in any accidents, its like anything we buy second hand its the risk we take, if the bike looks good feels good then and you can't find any damage on it then go for it if the price is right.
I agree with Ash...if it starts nice, sounds nice, and rides nice the chances are it is nice. If the price is nice that would be nice too.
If I was a seller( and I sold quite a few) and I had someone wanting to do a leakdown test I would just move on to the next buyer, just not worth the trouble but that is just me I guess.
I agree with Ash...if it starts nice, sounds nice, and rides nice the chances are it is nice. If the price is nice that would be nice too.
If I was a seller( and I sold quite a few) and I had someone wanting to do a leakdown test I would just move on to the next buyer, just not worth the trouble but that is just me I guess.
If I was a seller( and I sold quite a few) and I had someone wanting to do a leakdown test I would just move on to the next buyer, just not worth the trouble but that is just me I guess.
Jeez, I don't see it as an issue, just a new and better form of the old compression test. Pull the plugs, a bit of compressed air down the cylinder for a few seconds and done. No starter repeatedly whirling over as with the comp. test.
Would you also object to someone wanting to compression test an older bike?
Yes, I bought one in 2003 and one in 04. My wife and I had plans to do a lot of touring on the Vincent. Thinking the first bike would be somewhat unreliable due to it's advanced age, I thought it would be good to have a back up machine. The thinking was if a big trip was planned to the UK for example, air freight and our air travel prepaid, then it would be a bit of a disaster if the bike had a major breakdown just prior to leaving.
My fears were unwarranted, the back up bike hasn't been needed in 90,000 kms of touring, so I'm selling it. It is as new internally and externally.
"I" will take apart "MY" bike ......................... the next guy can take apart "HIS" bike.
Way too complicated, and potentially damaging ........................ to allow some stranger that much intimacy with "MY" motorcycle.
Then just to turn around and say ............. "thanx ............. I'll give it some thought. Oh .......... sorry bout that small chip in the tank paint. But it is hardly noticeable anyway. Just one more thing ............. I couldn't figure out where this one "thing" goes. It still runs ........... guess it isn't needed.
Again ............. I'll think about it. "
Really!?
You think it is perfectly FINE to put somebody through that?
Do you really think it will end there? Be that simple? That easy?
99% of people buying a motorcycle wouldn't even know what good numbers look like on a leak down.
Those same people don't even look into the gas tank. And IF they do, they are checking to see how much gas they get with their purchase.
Why stop there ............... may as well pull the wheels for the guy. That way he can stick his finger in the wheel bearings, looking for early stage "roughness" ............ that he may not "feel" by simply lifting the bike and giving the wheel a simple spin.
For every PITA that wants to dissect YOUR bike, in the name of "Maybe I'll buy it" ................. there are "AT LEAST" 100 more that will throw down cash ............... and know what to look for.
YEAH ! No big deal ........... take apart "MY" bike.
"F" that. Go buy a Honda.
Well I do a leakdown test before buying and it is simple. No objections from sellers so far and not much room left in my shop. I've only passed on one bike. Bike looked beautiful but too much leakage for me.
Guy that bought it went for the cosmetics and the seller's BS, he really got screwed, in effect paid for it twice by the time it was put into useable condition (Vincent)
Joeysan ................ the fact that you asked that question indicates that you WANT to learn, and are currently limited ............ in terms of "intimate experience with an engine of any type".
Nothing at all wrong with that. We all have different backgrounds ............ even if some passions overlap, we are different.
It has already been pointed out .................... there is a certain amount of "acceptable risk" involved in buying something "previously owned".
Hell ............. there is even a risk in buying Brand New.
Reality ................... do the best that you can at interpreting "what you CAN see" ............. and base your decision.
22K miles is considered Low Mileage. Although that mileage combined with only 2 oil changes would be catastrophic.
The answer to your question is much longer than anybody wants to type out. So you will be shorted.
The best answer thus far is ................ "compression test will do but if it runs good at that low millage it should be fine.They often go 100,000 miles."
THIS .............. is your answer. If that satisfies you ...... great, enjoy the bike.
If not ............ find somebody locally to look at it with you, or for you. There are a number of things to look for, that will indicate many things.
But the risk is still there ......... simply reduced a little.
Even a leak down isn't definitive ............ nor does it guarantee you of anything.
If you need further reassuring ............. feel free to PM me. We can speak over the phone ............ I do not feel like typing three pages of "What to look for's" and what they indicate. The overall picture will tell you about the owner, as much as about the bike. Which indicates how it was maintained ........... despite what you are told by the owner.:wink2:
Yeah, I certainly didn't mean to offend anyone with the leakdown test suggestion. They are a good test. I guess the bikes I've purchased have mostly been from people who know me, or we at least have mutual friends.
It's true not everyone has a careful approach to mechanical work.
You wouldn't want this guy attempting to fix your car or bike-
Check to see if the clutch slips or drags and if it engages smoothly. If it's going to slip that will most likely show up in top gear around where Max torque is.
Do the brakes work well or is there pulsation or chatter due to worn rotors?
Does the motor pull well and is there any trace of smoke on hard acceleration? Does it rev cleanly and pull to the red line then settle down to a steady idle at a light?
See that the trans is shifting up and down OK.
You might also check how the suspension is working properly. For example, if it bottoms easily front or rear on mildly rough pavement, then it will need some help here.
I'm not suggesting beating on the bike in a test ride, just ride it normally and pay attention to what is happening.
If some problems do show up on the test ride, it may still be a worthwhile machine, but at least you have a good idea of what you are faced with.
Firstly you would do a compression test first. A leakdown test is done after if a difference isfound with the comp test. The plugs have to be checked which can be done, obviously. Oily, fuelly tells you something. Whilst the general principles of the two tests are easy correct execution can be flawed. A comp test needs the motor to be turned multiple times till a stable reading is achieved. As mentioned a leakdown test needs to be done with both valves closed and you need to stop the motor turning. You could stick something down the plug hole for tdc, take a punt on which valves are closed. Ideally take the cam cover off then you can also check the clearances.
In reality if she dont smoke starts easy hot and cold and the price is right buy her. Of more importance are tyres, chains, sprockets as these can soon addup.
If you want a shop to check. They will just ride listen and visual once over and the seller is hesitant, look elsewhere. Plenty about!
I wouldn't do a damn thing other than ask the seller if he minds you booking an hour inspection in a shop you trust.
If the seller balks, you walk.
If the report is good you've got peace of mind.
If the report is negative you've either got a heads-up on avoidance or leverage for a killer deal.
:2cents
In 32 months I've done just under 30k miles and it's all good. Just put gas in and change oil at 4500 mls. Still runs great
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