Hi all.

How do you test, if you have a defective front bearing?

I've read about allowing the engine run at idle speed at then spray some oil between the flywheel and front bearing. If the engine stops, its because of a defective front bearing because the engine sucks air through the bearing.

I tried it on this monday engine that just flame randomly. Could it be because of a defective bearing?

As you can see in the video, its flames right after spraying oil on the bearing.

Defective engine

I wasn't sure if the method was reliable, so I tested it on my BTT engine with brand new bearings (only broken in). Guess what, it flames in the same way as the other engine after I sprayed oil on the bearing.

So, did I make the oil/bearing test correct?

front bearings have no way to seal the engine...the leak is coming from inside the engine and no bearing will stop it...the partial answer is to block the Bypass port inside, and the final solution is a Buku dust cap.......

Yes, it is the right test. I use breakeclean. What your doing when spraying is that engine will suck in the gass in the spraycan, witch in turn removes oxygen and the enigne will stall.

Is your +4 engine used, or is it brand new? Sometimes, engines is abit out of tolerance, so the hole were crank rotates is a bit to big. That in turn will make your engine suck in "unmessured" air, ie, it does not go through thr carb. Your engine will be difficult to tune and unstable, even with new bearings. Bearings is not airtight :-). Onroad engines f.eks. use steel shield bearings, but perform very well. As i said, the seal is between the crankcase and crank, not in the bearing itself. I would say your engines is "worn" but not so worn it is broken.

That is why the BUKU cap is sooooo nice. I would suggest you buy and test. It will help with tune and how stable it is. I am not shure if it helps to use RTV to seal the wacumehole under the carb, but you could try. Engines that i have used Buku on, does not stall like your engine does.

Reason the wacumhole under the carb, is to have a dry front bearing. To many people screems and complaines when the fornt bearing is moist but in reality, it does not meen anything at all, regards in what shape your front bearing is.

Test and you will see the light.

Lille-bror, Unfortunately ,you have done the test correctly. On the Werks Engine ( assuming EVERYTHING else is mechanically sound) that front bearing is the cause of all your random flaming and tuning issues. I have been there done that with the Werks engines. Running a much hotter plug will help reduce the issue but the fact is its still MASKING the problem...leaking front bearing... Notice I did not say BAD front bearing. Bearings in these engines are not seals... And this issue is by no means isolated to Werks engines. In fact your BTT just proves that point. I have tested for vacuum leaks on brand new never ran nova plus 4's. The first 2 tanks 250 cc's they passed the break cleaner test with zero issues. By tank 3 the engine was studdering. On the 4th tank, 500 cc's i could kill the engine instantly. This was with brand new nova 17011 bearings. So by the time we finish the break in process we are already masking a leaking front bearing with carburetor jetting. This problem is becoming more and more common place over the last couple years for many reasons. Fuel with less oil content / Engines that turn massive rpm / Running a lean bottom to get run time,which in turn requires a small idol gap. Dirty air filters.

Nothing is wrong with your motor by using that test, I have brand new OS Speeds and seen many motors will flame out unless they are very lucky, bearings don't make good airproof seals and were not made to be when vacuum is created inside crankcase, it's eventfully gonna happen. Doesn't mean anything is wrong but that Buku dust caps are the best idea that more people should use for sure. Again it's pretty normal but buy the Buku caps to stop it.

Add answer above is correct also

Thanks a million gentlemen :-)

The Werks has been a problem since day one. Has only 1 gallon through it, and is in great shape. But, we just can't get rid of the flames-outs. Tried different fuel, plugs (from OD77t to Novarossi 7 and Werks, all kinds of tuning, pipes etc etc.
Just changed the front bearing and will see how it turns out :-)
I'm not trying to harm the Werks brand, but would like to see the engine without any issues (not my engine - just trying to help a friend)

My BTT is a hole other story: put together with parts from 3 engines, and Raya did a fantastic job bringing the sleeve back to life
Crank is approx. 4 gallons old and I've no issues with idle or anything else.

Thanks for the Buku tip. Will give it a try :-). Will the thing fit between the engine and a Xray '13 clutch?

Flame outs can be caused by many things like fuel and bad headclearance. Sometimes even a different carburator can solve such an issue.

+1 on the carb...

Is "bad front bearing" an overdiagnosed problem, with the real problem being something else? At one of the races I went to this year a lot of people were flaming out, and one of the local engine gurus was running around fixing it. He wasn't changing the bearing..., but opening the idle gap. I observed this in the buggy final where I was pitting. The guy I was pitting for had an RB and said it ran perfectly and never needed to have the needles touched. Sure enough, 5-10 minutes in started flaming, and the dude cam over and opened the idle, and on he went for 20 more minutes in the final with zero issues. This happened on a few buggies in that race.. My engine had kept flaming in the truggy final before, to the point where I gave up and just bowed out. A couple weeks later I ran the engine again, opening the idle a bit, and it was fine..

When you run WOT or do a quick WOT blip to clear a short run up, You are pulling a lot of vacuum. Most of which is coming threw the carb.Unfortunately the time frame between you letting off the throttle (return to idol) or breaking you go from somewhere between a 6-9mm opening in the carb down to some where between .3 and .7 now your pulling massive amounts of vacuum (this is when vacuum levels are at its highest) and since it cant get threw the carb it gets pulled threw the front bearing. Opening the idol gap will/can fix the flame out issues. But it does not change the fact that your pulling unfiltered air into your engine..

Now you start a race with a leak but you have the engine tunes accordingly to counter your leak... 10 15 minutes into your main your air filter starts getting dirty/ clogged. Guess what? The engine is now struggling to get the proper air needed for your current needle settings so it pulls more vacuum threw the front bearing and you have an engine that just RANDOMLY flamed out!

Just saying, I've noticed over the last several years people preaching more and more about the need for both smaller and smaller idle gaps, along with smaller and smaller venturis.., and I'm just kind of dubious about needing to change bearings (and rods) as frequently as some people make out..

No, you are correct. Idol gap size (or lack of) is a direct contributor of the issue at hand. Rods... well its easier and cheaper for engine factories to have larger tolerances between pistons and sleeves than tighter tolerances Look at OS and werks easy break in and closer tolerances. How often are those rods blowing?

People running small venturies is just asking for trouble. Engine just gets difficult to tune, run a bit hotter and will change its tune faster so you need to retune. I just stopped using 6 and never run smaller than 7

Is saud by Philly, small idlegaps is needed because your engine leans out when it is up to proper temp. That is after 12-15 minutes of runtime. ( abaut 9-12 give or take a bit into the main finale). What happend after aprox 15 minutes into the main is that people is starting to flame. They run their engines to lean becasue it is tuned during a qual.... Remeber that the chassis is a huge cooling aera that needs some time to heat up.

I wish that people started to practice engine tuning also :-)

Learning what each brand and even specific engine type you run needs tune wise is most likely the biggest issue, then cleaning is another one. I see some pretty dirty engines at the track. Imagine what the inside looks like. then clutches. I see all kinds of wonky clutches too. maintain your clutch. Then glowplugs. I see so many superhot glowplugs that burn up in one run.

a good example by types of engines needing different tuning is the Plus-4. If you tune it to have a low idle it most likely will flameout. Don't be afraid to lean it a bit on bottom. it can be a fine adjustment. It takes lots of wrk to make each engine work properly. If the work is not put in.... the engine will suck. If you treat your engine like a beat up lawnmower it will run like one.

Oh yeah, brakes. If you run your brakes so strong it will stand on it's nose you are asking for trouble. the clutch is still engaged when you are doing nose stands. Flame. Fuel. If you use crappy fuel your engine will hate you.

Running the engine too lean to get 15 minute runtime on 7% oil fuels. well that can cause issues right.

Fat bottom ends. haha. Kills it every time. Fuel tanks that don't seal are difficult to figure out but easy to fix.

dirt in the engine. Clean it. You dirty glowplug hole people know what I mean.

I had a bad front bearing just now, and what I found most striking was that it idled like a motor boat, "woooar wooooar woooar" instead of one steady "woooooaaaaaaaaaaerrrrrr" sound it was constantly changing.

So if that helps for anyone, that might be a trick, listen if it motorboats or not.