Having spent lots of time and not a little cash trying to cure a repeating case of running on one cylinder, I recently learned that my bike is producing a constant whiff of burning oil from the nearside pot, eventually oiling up the spark plug and misfiring.
My initial thought - the bike might need a rebore but I learned today that this is not possible with my Guzzi as the bores are Nikasil lined. I’m told that removal of the appropriate cylinder head will reveal any damage to the bore if that’s where the problem lies and the solution is to take or send the barrel to a specialist to have it relined.
A couple of questions - would I be advised to have both barrels done -and is there a “go to” company recommended - I am in North Kent.
The bike, a 1979 V50 2 shows just under 50k on the odometer , is this likely to be well below the bikes genuine mileage?
I would give it an compression test and compare the result of the two cylinders, if its down it will need locking at but if the compression is similar it could be valve guide oil seals leaking on that side, just a thought.
Nikasil (or Nigusil) is near-impossible to replace for a reasonable price, if you can find anywhere that can do it with the correct percentages of silicon etc. in the mix. Secondly, to the best of my knowledge Guzzi never provided steel-linered barrels for the small blocks. Getting that done would be easy enough - any competent engineering shop can do that for you - but then you have the problem of running very hard rings designed for nikasil in a relatively soft steel barrel. The barrel won’t last long.
If it turns out to be the bore, Gutsibits will sell you a good one for between 30 and 80 quid and will get it vapour-blasted for you for a few quid more.
I’m with Schwerzer in suspecting valve guides or valve guide oil seals. Go the easy route first.
(For any big-block rider wondering about steel rings in a nikasil barrel - yes, that’s okay. Info from the now-defunct Motomecca Spares when I could go in on a Saturday morning and scab a mug of coffee off the counter staff).
Valve stem oil seals or worn guides seem the most likely culprit.
Pull the head off and have a look at the guides and seals, if the Nikasil is worn through it will be obvious. There are a few companies in the UK that offer this, all the classic racers using TZ250’s and 350’s get their barrels recoated periodically. A second hand barrel will undoubtedely be cheaper
Many thanks Schwerzer, DaiG and Russell for your responses. I borrowed a compression tester today and the left pot measured 60 psi, the right pot 90 psi. I haven’t gone any further with it other than to ask Gutsibits if they have a suitable replacement should I require one. However I also found that there is an intermittent ignition fault which I will investigate tomorrow.
That seems very low compression on both sides, I think from memory I was getting 120+ psi.
The valves may not be seating properly but that wouldn’t cause smoking, one trick I’ve heard of is to squirt oil into the barrel and check the psi again to see if it has increased any, I think this shows its the bore/rings are the problem.
When you did the compression test did you open the throttle to the stop, if not it will not give the correct reading.
Don’t know if it’s of any help but I had my cylinders reNikasiled if that’s a word, by Richard Moore at Moorespeed . He’s a BMW airhead specialist . I had new light weight Omega pistons fitted to some high mileage barrels that required the old worn Nikasil to be removed, and replated, after the barrels had been rebored. This was to ensure optimal running clearance for the significantly higher compression of the new pistons. Didn’t use any oil after the rebuild which included cylinder head work.
The Nikasil replacement wasn’t expensive when I had the work done about 7 years ago. I’m contemplating doing the same thing on a different Bmw at the moment, if that’s a recommendation.
Have a look at his site, it might be worth a phone call. He’s usually pretty busy……
Another possibility to think about, piston rings lose their springiness over time, apparently if 40+ years old they could do with being changed. (Source: Superbike Surgery.)
Given the low comp etc. I would want to take it apart for a coating of looking at, rather than make guesses, then you can examine valve guides, look for worn through patches on the bore(s), etcetera…
I did rather rush this bit but at least established that there is a significant difference between the two sides. I called my local BMW expert to find out if he had any experience having bores re done with Nikasil as the airhead boxers featured this development from 1981 on, and yes he has had several restored by Langcourt to his satisfaction.
Jim has some experience with Guzzis and is going to sort mine out as I seem to be chasing my tail; solving one issue only to create another! Will report the outcome when its done. Thanks fo all the help everybody!
Do your research; I can’t recall if the small block twins were nikasil or nigusil. There’s a different percentage of silicon in the two mixes and that will make a difference on ring longevity.
Thanks again DaiG I’ll pursue this with Jim Cray next week but in the meantime an earlier issue has raised itself again! You responded to my note saying that my bike had gone onto one cylinder after a ride of about 40 miles - my first trip on it back in early May and you suggested that I check the igniter contacts which I did after a little misunderstanding. It didn’t as I recall entirely sort the problem and I subsequently replaced one of the coils in the belief that the older of the two (original) was breaking down when hot. However after many hours of messing about with carburetters I thought my problems were solved! Not so! I have done about 250 miles on the bike so far and all seemed to be going well until last Saturday. I was on the West Kent Run and rode about 50 miles to the lunch stop without incident but on the way home after about 20 miles the bike went onto one cylinder for a few minutes and then picked up again. It repeated this several times and I presumed that it was fuel starvation though it never completely stopped. It got worse the farther I travelled - cutting out on one pot then picking up for a short distance til eventually it didn’t pick up at all and I managed to limp home.
I noticed that I could just about put my hand on the top of the nearside pot for a brief moment but the offside pot was far too hot to do that. I then removed the cool plug and checked for a spark - nothing! However I later tried again and there was a very healthy spark and the bike started and ticked over at a steady beat.
Maybe I’m once again jumping to conclusions but having done a bit of research I’ve learned that the igniters can fail if they get hot! On saturday the bike was parked in direct sunlight and here in Kent the afternoon temperature was over 30C.
However, this item is no longer available new and used items are on offer at £90 or more each.
Any suggestions as to my next course of action would be appreciated (again!)
Heat breakdown was the first thing that came to mind while I was reading your post. You may want to widen your ebay search to include Laverda as well because some models used the same ignition parts and for some reason, they tend to be cheaper secondhand! Of course there’s no guarantee that you won’t get the same problem.
There are two solutions that I can suggest, but neither is cheap. One is to drop a Mk3 engine and wiring loom in there and yes, that would work out cheaper than buying the separate parts to do the conversion. The big problem you are up against with a parts conversion is that your engine has a duplex timing chain and the Mk3 has a simplex chain, so even before you get started you need camshaft, crankshaft, oil pump sprocket, timing chain… Nope.
The other solution is equally as pricey and, I have to admit, surprised me no end. The Elektronik Sachse ignition system that fits on the Bosch alternator for the big block engines also fits the small block engines. As of today, €392.62 equals £336.38.
So… you need to be sure it is heat-related breakdown. So that we don’t get at cross-purposes, what are you talking about when you say ‘igniters’? The bit at the front of the engine or the bit under the sidepanel?
Hi again DaiG - first things first - I’m definitely referring to one of the two Bosch igniters/amplifiers which are located behind the two side panels.
There’s been a welcome development! This morning after I’d written my piece I called Gutsibits even though their website didn’t look too promising. I wanted to know if they had any used ones sculling about and so Jo spent a little time looking through their used stock lists. Even whilst I was patiently waiting he suddenly noticed that one had popped up on his system - new - did I want it at about £80 - given that used ones are on offer on Ebay fo more than that I said yes and he confirmed that the picture of the item bore the same Bosch part number as the one I’m wanting to replace on my Guzzi, Only one snag - its coming from a shop in Italy where apparently a few of them have cropped up so I’ll have to wait a couple of weeks. Meantime I could still use the bike for short trips. Jo’s also looking to see if there’s a suitable barrel in the used parts warehouse.
Further item! When I bought the bike I planned to fit a Silent Hecktik ignition system. I fitted one to my previous bike - a BMW Boxer - it was utterly reliable. It wasn’t cheap, about £250 in 2007 but the old bike did about 10% more to the gallon once fitted so over the next 50,000 miles I clocked up , it more than paid for itself. However the last price for the Guzzi I saw was well over £400 and not available until the autumn of 2026. So maybe I’ll leave well alone if appropriate - we shall see!
Good news on the igniter So you can do the following test:
Find a hot air gun
unbolt BOTH igniters so they are hanging in the breeze
Start the bike
Fry the igniters one at a time with the hot air gun until one or the other breaks down (or not).
I did check on Silent Hectik ignition systems but they are for replacing points systems only i.e they locate on the camshaft using the original locating peg to drive the reluctor (pickup). Not much use to you.
I’ve been forced to buy both a Monza camshaft and a duplex timing chain from Italy recently, plus a crankshaft and shells from the Netherlands. There was nothing available anywhere in the UK for the older duplex timing chain engines. If your engine hasn’t already got it and you have a bit of spare cash, fit an auto-tensioner to the timing chain. It prolongs the life by stopping the chain from slapping around.
Not sure I see the point in your proposed test ? I am satisfied that the problem is confined to the nearside cylinder and that the igniter supplying the spark to that pot is on the same side. As I will be fitting a new igniter in its place I will expect it to work; similarly the offside igniter is currently working ok anyway! I will be at a loss for an explanation if the new igniter doesn’t solve the problem once and for all.
It was just so you could be absolutely sure it’s the igniter and not the pickup. The pickups sit right under an exploding fuel-air mixture and are mounted in such a way that the wires are forced through 90 degrees immediately they exit the pickup casing. I’ve seen a few that have split the insulation literally at the exit point and a couple that had also split the copper. That bike was still running (badly) because the rear of the insulation was still in one piece and physically holding the broken wire together. If the camshaft or crankshaft seal has decided to weep, you can throw corrosion products into that mix.
What I have done with damaged pickups is to ensure they are totally degreased, then ease the wires back to an exit angle of about 45 degrees. After that, build up a supporting base with 24 hour Araldite that covers any splits in the insulation and helps support the wires through the last 45 degrees to exit the timing chest.
Am I blind or nobody blames overheated coil as a potential and probable reason. Old coils give up as well when temperatures get high. Easy to swap to make sure where’s the blame.
Not re-lined, re-plated. Any Nikasil barrel is a one-off proposition - you’re not even meant to change piston rings on a worn bore.
However, guess what? You can. Take off the head & bore (careful with the pistons, and block the mouth of the case with a clean cotton rag). Take off the top ring (carefully, do not twist it - do the old card trick). Then, insert it at the top of the bore parallel to the cylinder face, at 10-20mm down the bore, then at half depth, then at the bottom of the piston travel point (you will see the wear marks) and at each point, measure the ring gap. Look at the specs, and check the tolerance from the manual.
I ended up just buying a new ring set and replacing them on each cylinder, and ignoring the manual. No more oil burn, and the bike ran perfectly OK on “worn barrels”.
So you can do the following test: