FlyingG
Hello Gents,
I'm trying to get my 851 back together after sitting in pieces for several years. The goal is a nice, fun (hopefully reliable) street/track day bike. I've already buttoned up the cases (crank balanced to Carrillo rods & FBF 94mm pistons). I'm working on the heads now & have several questions/concerns...
First, I pulled the tray with my valve train parts, & - voila! - the cams have a very, very light patina of rust on them. Are they trashed or can they be cleaned up? If can be saved, by what procedure? If trashed, what are my options?
Next, while the heads are bare, I believe I should have them decked - not for more compression ( I'm already worried about too much for the street with the FBF pistons), but just to be sure the surface is flat & smooth to get a good gasket seal.
I know some of you have skimmed the heads to raise compression in lieu of domed pistons (& I understand why perfectly; I bought the FBF's in a moment of weakness). How much machining results in how much compression difference? Hard to calculate, since the combustion chamber shape is irregular. Haven't cc'd anything yet.
Are the Snyder Maintenance guides worth the money?
Finally for today, I don't seem to able to see most photos or documents in the posts, just a little icon that doesn't do anything. Any ideas what to check?
Any help you could give would be most, er, helpful. Thanks.
Sorci851
Hello,
Although this is hind sight, I hold off rust on my future engine project components by coating the parts with WD40, and putting the parts in plastic bags. You can remove rust safely with Rustol without any effort (available from Sudco.com). Since cam shafts typically have a hard surface coating, I would NOT do any scrubbing to remove the rust for fear of compromising any surface coating.
Unless the engine overheated, resulting in head warpage I wouldn't do any skimming of the surface. Your Ferracci pistons are likely 12.5:1 already, and skinning the head surface will raise that compression even further. I would just make sure the surfaces are clean, set the squish with the proper base gaskets, and put it all together. The reason why a lot of members here skim the head surfaces to increase compression rather than replace the pistons with high-comp pistons is 1) it requires less work, 2) you get better flame travel with the flatter stock pistons. Also, simply installing 748 heads bump up compression as well.
The LT Snyder manuals are great for learning about a lot of short cuts on maintenance and repairs; I have the Desmoquattro manual, and feel its worth the money. I also use the Haynes 916 service manual since the procedures largely apply to the 851/888 bikes. Also, ask Mr.R here on the forum, and he will give you all the tech info. you need.
Justin
FlyingG
Thanks for the reply, Justin.
I had to get new pistons anyway since I was going for 2mm over, & those happened to be available at a good price, as I recall. What pistons have others used when going from 92 to 94mm? Stock 888/916? Seems like aftermarket flat-top 94mm pistons are pretty elusive these days.
I took a closer look at the horz intake cam (w/ the tacho drive), & it actually looks good, with just a tiny stain on the RH intake lobe. Whew! The shaft extending out is a little rusty, though. I'll check into the Sudco stuff. Everything was well-coated with oil when put up, but obviously it's all drained/flashed off. Or it could be the corrosive nature of mouse wee.
FWIW, my old 750SS racer once broke a closer spring & took a few chips out of the lobe surfaces my Vee-two cams (just left them out altogether after that - the springs, not the cams :-) Continued to run them for years with zero problems to rockers or further wear of the cam! I loved that bike, but I got tired of trying to scaring up new cases all the time in those pre-eBay days. I wanted to built a 750 out of 900 motor - would have gotten bigger valves & 6-speeds, & it probably would last forever.
Anyone else have problems seeing the pics in the posts? Thanks.
dididucdich
If you mean older posts I have the same problem - I see nothing but can read the comments 😳
hindsight
FlyingG wroteAre the Snyder Maintenance guides worth the money?
I'd say so. I've got the third edition, and am considering upgrading to the fourth edition (partly because of the 1098 that I've got at the moment). Certainly it's a good "real world" reference.
FlyingG
Thank you, gentlemen. This is very helpful. I'm sure I will have plenty more questions as things progress. Cheers.
marvin
To clean the cams I would use a scotch brite pad and some WD40 or similar. A fine scotch brite pad won't remove the hard surface.
I use a cast iron lap plate and 400 grit carborundum to
"flatten" my heads (just to make sure they are really flat) You could probably do about the same using a surface plate and a sheet of 400-500 wet or dry paper.
